TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
DIntegrated Asynchronous-Communications
Element
DConsists of Four Improved TL16C550C
ACEs Plus Steering Logic
DIn FIFO Mode, Each ACE Transmitter and
Receiver Is Buffered With 16-Byte FIFO to
Reduce the Number of Interrupts to CPU
DIn TL16C450 Mode, Hold and Shift
Registers Eliminate Need for Precise
Synchronization Between the CPU and
Serial Data
DUp to 16-MHz Clock Rate for up to 1-Mbaud
Operation with VCC = 3.3 V and 5 V
DProgrammable Baud-Rate Generators
Which Allow Division of Any Input
Reference Clock by 1 to (216−1) and
Generate an Internal 16 × Clock
DAdds or Deletes Standard Asynchronous
Communication Bits (Start, Stop, and
Parity) to or From the Serial-Data Stream
DIndependently Controlled Transmit,
Receive, Line Status, and Data Set
Interrupts
D5-V and 3.3-V Operation
DFully Programmable Serial Interface
Characteristics:
− 5-, 6-, 7-, or 8-Bit Characters
− Even-, Odd-, or No-Parity Bit
− 1-, 1 1/2-, or 2-Stop Bit Generation
− Baud Generation (DC to 1-Mbit Per
Second)
DFalse Start Bit Detection
DComplete Status Reporting Capabilities
DLine Break Generation and Detection
DInternal Diagnostic Capabilities:
− Loopback Controls for Communications
Link Fault Isolation
− Break, Parity, Overrun, Framing Error
Simulation
DFully Prioritized Interrupt System Controls
DModem Control Functions (CTS, RTS, DSR,
DTR, RI, and DCD)
D3-State Outputs Provide TTL Drive
Capabilities for Bidirectional Data Bus and
Control Bus
DProgrammable Auto-RTS and Auto-CTS
DCTS Controls Transmitter in Auto-CTS
Mode,
DRCV FIFO Contents and Threshold Control
RTS in Auto-RTS Mode,
description
The TL16C554A is an enhanced quadruple version of the TL16C550C asynchronous-communications element
(ACE). Each channel performs serial-to-parallel conversion on data characters received from peripheral
devices or modems and parallel-to-serial conversion on data characters transmitted by the CPU. The complete
status of each channel of the quadruple ACE can be read by the CPU at any time during operation. The
information obtained includes the type and condition of the operation performed and any error conditions
encountered.
The TL16C554A quadruple ACE can be placed in an alternate FIFO mode, which activates the internal FIFOs
to allow 16 bytes (plus three bits of error data per byte in the receiver FIFO) to be stored in both receive and
transmit modes. In the FIFO mode of operation, there is a selectable autoflow control feature that can
significantly reduce software overhead and increase system efficiency by automatically controlling serial-data
flow using RTS output and CTS input signals. All logic is on the chip to minimize system overhead and maximize
system efficiency. Two terminal functions allow signaling of direct-memory access (DMA) transfers. Each ACE
includes a programmable baud-rate generator that can divide the timing reference clock input by a divisor
between 1 and 216 −1.
The TL16C554A is available in a 68-pin plastic-leaded chip-carrier (PLCC) FN package, 64-pin plastic quad
flatpack (PQFP) PM package and in an 80-pin (TQFP) PN package.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
Copyright © 2010, Texas Instruments Incorporated
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
2POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
28 29
DSRD
CTSD
DTRD
GND
RTSD
INTD
CSD
TXD
IOR
TXC
CSC
INTC
RTSC
VCC
DTRC
CTSC
DSRC
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
30
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
DSRA
CTSA
DTRA
VCC
RTSA
INTA
CSA
TXA
IOW
TXB
CSB
INTB
RTSB
GND
DTRB
CTSB
DSRB 31 32 33 34
FN PACKAGE
(TOP VIEW)
D2
D1
87 6 5493
RXA
GND
D7
D6
D5
D4
D3
XTAL2
RESET
RXRDY
TXRDY
RXB
NC
A2
A1
A0
XTAL1
168672
35 36 37 38 39
66 65
27
DCDB
D0
INTN
64 63 62 61
40 41 42 43
GND
RXC
RIC
DCDC
RXD
RID
DCDD
DCDA
RIA
VCC
RIB
VCC
NC − No internal connection
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
3
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
23
DSRC
DCDC
RIC
RXC
GND
RESET
XTAL2
XTAL1
A0
A1
A2
VCC
RXB
RIB
DCDB
DSRB
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
4
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
DCDD
RID
RXD
VCC
D0
D1
D2
D3
D4
D5
D6
D7
GND
RXA
RIA
DCDA 5678
PM PACKAGE
(TOP VIEW)
TXC
CSC
47 46 45 44 4348 42
DTRD
GND
RTSD
INTD
CSD
TXD
IOR
TXB
CSB
INTB
RTSB
DTRA
RTSA
INTA
CSA
TXA
IOW
40 39 3841
910111213
37 36
1
DSRA
INTC
RTSC
35 34 33
14 15 16
GND
DTRB
CTSB
DTRC
CTSC
DSRD
CTSD
VCC
CTSA
VCC
NC − No internal connection
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
4POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
23
NC
DSRB
CTSB
DTRB
GND
RTSB
INTB
CSB
TXB
IOW
NC
TXA
CSA
INTA
RTSA
VCC
DTRA
CTSA
DSRA
NC
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
4
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
NC
DSRC
CTSC
DTRC
VCC
RTSC
INTC
CSC
TXC
IOR
NC
TXD
CSD
INTD
RTSD
GND
DTRD
CTSD
DSRD
NC
5678
PN PACKAGE
(TOP VIEW)
XTAL1
59 58 57 56 5560 54
RIC
RXC
GND
TXRDY
RXRDY
RESET
NC
D3
D5
RID
RXD
NC
INTN
D0
D1
D2
52 51 5053
910 11 12 13
49 48
1
NC
A0
47 46 45 44
14 15 16 17
D6
D7
GND
RXA
A1
A2
XTAL2
RXB
NC
DCDC
RIA
DCDA
18 19 20
RIB
DCDB
43 42 41
VCC
NC
NC
CC
V
DCDD
D4
NC
NC − No internal connection
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
5
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
functional block diagram (per channel)
Receiver
Buffer
Register
Divisor
Latch (LS)
Divisor
Latch (MS)
Baud
Generator
Receiver
FIFO
Line
Status
Register
Transmitter
Holding
Register
Modem
Control
Register
Modem
Status
Register
Line
Control
Register
Transmitter
FIFO
Interrupt
Enable
Register
Interrupt
Identification
Register
FIFO
Control
Register
Select
and
Control
Logic
Interrupt
Control
Logic
S
e
l
e
c
t
Data
Bus
Buffer
RXA
TXA
CTSA
DTRA
DSRA
DCDA
RIA
INTA
11
12
10
9
8
15
17
7
16
A0 34
D(7 − 0)
5 − 66
Internal
Data
Bus
33
32
20
50
54
37
52
18
39
35
36
38
65
A1
A2
CSA
CSB
CSC
CSD
RESET
IOR
IOW
XTAL1
RXRDY
S
e
l
e
c
t
Receiver
Shift
Register
Receiver
Timing and
Control
Transmitter
Timing and
Control
Transmitter
Shift
Register
Modem
Control
Logic
8
13, 30, 47, 64
6, 23, 40, 57
VCC
GND
Power
Supply
RTSA
14
Autoflow
Control
(AFE)
8
8
8
8
8
8
8
TXRDY
XTAL2
INTN
NOTE A: Terminal numbers shown are for the FN package and channel A.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
6POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Terminal Functions
TERMINAL
NAME FN
NO.
PM
NO.
PN
NO.
I/O DESCRIPTION
A0
A1
A2
34
33
32
22,
23,
24
48
47
46
IRegister select terminals. A0, A1, and A2 are three inputs used during read and write
operations to select the ACE register to read or write.
CSA, CSB,
CSC, CSD
16, 20,
50, 54
7, 11,
38, 42
28, 33,
68, 73
IChip select. Each chip select (CSx) enables read and write operations to its respective
channel.
CTSA, CTSB,
CTSC, CTSD
11, 25,
45, 59
2, 16,
33, 47
23, 38,
63, 78
IClear to send. CTS is a modem status signal. Its condition can be checked by reading bit
4 (CTS) of the modem-status register. Bit 0 (ΔCTS) of the modem-status register indicates
that CTS has changed state since the last read from the modem-status register. If the
modem-status interrupt is enabled when CTS changes levels and the auto-CTS mode is
not enabled, an interrupt is generated. CTS is also used in the auto-CTS mode to control
the transmitter.
D7 − D0 66 − 68
1−5
53−60 15−11,
9−7
I/O Data bus. Eight data lines with 3-state outputs provide a bidirectional path for data, control,
and status information between the TL16C554A and the CPU. D0 is the least-significant
bit (LSB).
DCDA, DCDB,
DCDC, DCDD
9, 27,
43, 61
18, 31,
49, 64
19,42,
59, 2
I Data carrier detect. A low on DCDx indicates the carrier has been detected by the modem.
The condition of this signal is checked by reading bit 7 of the modem-status register.
DSRA, DSRB,
DSRC, DSRD
10, 26,
44, 60
1, 17,
32, 48
22, 39,
62, 79
IData set ready. DSRx is a modem-status signal. Its condition can be checked by reading
bit 5 (DSR) of the modem-status register. DSR has no effect on the transmit or receive
operation.
DTRA, DTRB,
DTRC, DTRD
12, 24,
46, 58
3, 15,
34, 46
24, 37,
64, 77
OData terminal ready. DTRx is an output that indicates to a modem or data set that the ACE
is ready to establish communications. It is placed in the active state by setting the DTR bit
of the modem-
control register. DTRx is placed in the inactive state (high) either as a result of the master
reset during loop-mode operation, or when clearing bit 0 (DTR) of the modem-control
register.
GND 6, 23,
40, 57
14,
28, 45,
61
16, 36,
56, 76
Signal and power ground
INTN 65 6 I Interrupt normal. INTN operates in conjunction with bit 3 of the modem-status register and
affects operation of the interrupts (INTA, INTB, INTC, and INTD) for the four universal
asynchronous receiver/transceivers (UARTs) per the following table.
INTN OPERATION OF INTERRUPTS
Brought low or
allowed to float
Interrupts are enabled according to the state of OUT2 (MCR bit 3). When
the MCR bit 3 is cleared, the 3-state interrupt output of that UART is in
the high-impedance state. When the MCR bit 3 is set, the interrupt output
of the UART is enabled.
Brought high Interrupts are always enabled, overriding the OUT2 enables.
INTA, INTB,
INTC, INTD
15, 21,
49, 55
6, 12,
37, 43
27, 34,
67, 74
O External interrupt output. The INTx outputs go high (when enabled by the interrupt register)
and inform the CPU that the ACE has an interrupt to be serviced. Four conditions that cause
an interrupt to be issued are: receiver error, receiver data available or timeout (FIFO mode
only), transmitter holding register empty, and an enabled modem-status interrupt. The
interrupt is disabled when it is serviced or as the result of a master reset.
IOR 52 40 70 I Read strobe. A low level on IOR transfers the contents of the selected register to the
external CPU bus.
IOW 18 9 31 I Write strobe. IOW allows the the CPU to write to the register selected by the address.
RESET 37 27 53 I Master reset. When active, RESET clears most ACE registers and sets the state of various
signals. The transmitter output and the receiver input are disabled during reset time.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
7
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Terminal Functions (Continued)
TERMINAL
NAME FN
NO.
PM
NO.
PN
NO.
I/O DESCRIPTION
RIA, RIB,
RIC, RID
19, 30,
50, 63
18, 43,
58, 3
IRing detect indicator. A low on RIx indicates the modem has received a ring signal from
the telephone line. The condition of this signal can be checked by reading bit 6 of the
modem-status register.
RTSA, RTSB,
RTSC, RTSD
5, 13,
36, 44
26, 35,
66, 75
ORequest to send. When active, RTS informs the modem or data set that the ACE is ready
to receive data. RTS is set to the active level by setting the RTS modem-control register
bit, and is set to the inactive (high) level either as a result of a master reset, or during
loop-mode operations, or by clearing bit 1 (RTS) of the MCR. In the auto-RTS mode, RTS
is set to the inactive level by the receiver threshold-control logic.
RXA, RXB
RXC, RXD
7, 29,
41, 63
20, 29,
51, 62
17, 44,
57, 4
ISerial input. RXx is a serial-data input from a connected communications device. During
loopback mode, the RXx input is disabled from external connection and connected to the
TXx output internally.
RXRDY 38 54 O Receive ready. RXRDY goes low when the receive FIFO is full. It can be used as a single
transfer or multitransfer.
TXA, TXB
TXC, TXD
17, 19,
51, 53
8, 10,
39, 41
29, 32,
69, 72
OTransmit outputs. TXx is a composite serial-data output connected to a communications
device. TXA, TXB, TXC, and TXD are set to the marking (high) state as a result of reset.
TXRDY 39 55 O Transmit ready. TXRDY goes low when the transmit FIFO is full. It can be used as a single
transfer or multitransfer function.
VCC 13, 30,
47, 64
21, 35,
52
5, 25,
45, 65
Power supply
XTAL1 35 25 50 I Crystal input 1 or external clock input. A crystal can be connected to XTAL1 and XTAL2 to
utilize the internal oscillator circuit. An external clock can be connected to drive the
internal-clock circuits.
XTAL2 36 26 51 O Crystal output 2 or buffered clock output (see XTAL1).
absolute maximum ratings over free-air temperature range (unless otherwise noted)†
Supply voltage range, VCC (see Note 1) −0.5 V to 7 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input voltage range at any input, VI −0.5 V to 7 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output voltage range, VO −0.5 V to VCC + 3 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Continuous total-power dissipation at (or below) 70°C 500 mW. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating free-air temperature range, TA: TL16C554A 0°C to 70°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TL16C554AI −40°C to 85°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage temperature range, Tstg −65°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
†Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTE 1: All voltage levels are with respect to GND.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
8POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
recommended operating conditions, standard voltage (5 V-nominal)
MIN NOM MAX UNIT
Supply voltage, VCC 4.75 5 5.25 V
Clock high-level input voltage at XTAL1, VIH(CLK) 2 VCC V
Clock low-level input voltage at XTAL1, VIL(CLK) −0.5 0.8 V
High-level input voltage, VIH 2 VCC V
Low-level input voltage, VIL −0.5 0.8 V
Clock frequency, fclock 16 MHz
Operating free air temperature T
TL16C554A 0 70 °C
Operating free-air temperature, TATL16C554AI −40 85 °C
electrical characteristics over recommended ranges of operating free-air temperature and supply
voltage, standard voltage (5-V nominal) (unless otherwise noted)
PARAMETER TEST CONDITIONS MIN TYP†MAX UNIT
VOH‡High-level output voltage IOH = − 1 mA 2.4 V
VOL‡Low-level output voltage IOL = 1.6 mA 0.4 V
IIkg Input leakage current VCC = 5.25 V, GND = 0,
VI = 0 to 5.25 V, All other terminals floating ±10 μA
IOZ
High-impedance output
current
VCC = 5.25 V, GND = 0, VO = 0 to 5.25 V,
Chip selected in write mode or chip deselected ±20 μA
ICC Supply current
VCC = 5.25 V, TA = 25°C,
RX, DSR, DCD, CTS, and RI at 2 V,
All other inputs at 0.8 V, XTAL1 at 4 MHz,
No load on outputs, Baud rate = 50 kilobits per second
50 mA
Ci(XTAL1) Clock input capacitance 15 20 pF
Co(XTAL2) Clock output capacitance V
CC
= 0, V
SS
= 0, all other terminals
g
rounded, 20 30 pF
CiInput capacitance
VCC
=
0
,
VSS
=
0
,
all
other
terminals
grounded
,
f = 1 MHz, TA = 25°C6 10 pF
CoOutput capacitance 10 20 pF
†All typical values are at VCC = 5 V, TA = 25°C.
‡These parameters apply for all outputs except XTAL2.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
9
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
recommended operating conditions, low voltage (3.3-V nominal)
MIN NOM MAX UNIT
Supply voltage, VCC 3 3.3 3.6 V
Clock high-level input voltage at XTAL1, VIH(CLK) 2 VCC V
Clock low-level input voltage at XTAL1, VIL(CLK) −0.5 0.8 V
High-level input voltage, VIH 2 VCC V
Low-level input voltage, VIL −0.5 0.8 V
Clock frequency, fclock 16 MHz
Operating free air temperature T
TL16C554A 0 70 °C
Operating free-air temperature, TATL16C554AI −40 85 °C
electrical characteristics over recommended ranges of operating free-air temperature and supply
voltage, low voltage (3.3-V nominal) (unless otherwise noted)
PARAMETER TEST CONDITIONS MIN TYP†MAX UNIT
VOH‡High-level output voltage IOH = − 1 mA 2.4 V
VOL‡Low-level output voltage IOL = 1.6 mA 0.4 V
IIkg Input leakage current VCC = 3.6 V, GND = 0,
VI = 0 to 3.6 V, All other terminals floating ±10 μA
IOZ
High-impedance output
current
VCC = 3.6 V, GND = 0, VO = 0 to 3.6 V,
Chip selected in write mode or chip deselected ±20 μA
ICC Supply current
VCC = 3.6 V, TA = 25°C,
RX, DSR, DCD, CTS, and RI at 2 V,
All other inputs at 0.8 V, XTAL1 at 4 MHz,
No load on outputs, Baud rate = 50 kilobits per second
40 mA
Ci(XTAL1) Clock input capacitance 15 20 pF
Co(XTAL2) Clock output capacitance V
CC
= 0, V
SS
= 0, all other terminals
g
rounded, 20 30 pF
CiInput capacitance
VCC
=
0
,
VSS
=
0
,
all
other
terminals
grounded
,
f = 1 MHz, TA = 25°C6 10 pF
CoOutput capacitance 10 20 pF
†All typical values are at VCC = 3.3 V, TA = 25°C.
‡These parameters apply for all outputs except XTAL2.
clock timing requirements over recommended ranges of operating free-air temperature and supply
voltage (see Figure 1)
MIN MAX UNIT
tw1 Pulse duration, clock high (external clock) 31 ns
tw2 Pulse duration, clock low (external clock) 31 ns
tw3 Pulse duration, RESET 1000 ns
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
10 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
read cycle timing requirements over recommended ranges of operating free-air temperature and
supply voltage (see Figure 4)
MIN MAX UNIT
tw4 Pulse duration, IOR low 75 ns
tsu1 Setup time, CSx valid before IOR low (see Note 2) 10 ns
tsu2 Setup time, A2 −A0 valid before IOR low (see Note 2) 15 ns
th1 Hold time, A2 −A0 valid after IOR high (see Note 2) 0 ns
th2 Hold time, CSx valid after IOR high (see Note 2) 0 ns
td1 Delay time, tsu2 + tw4 + td2 (see Note 3) 140 ns
td2 Delay time, IOR high to IOR or IOW low 50 ns
NOTES: 2. The internal address strobe is always active.
3. In the FIFO mode, td1 = 425 ns (min) between reads of the receiver FIFO and the status registers (interrupt-identification register
and line-status register).
write cycle timing requirements over recommended ranges of operating free-air temperature and
supply voltage (see Figure 5)
MIN MAX UNIT
tw5 Pulse duration, IOW↓50 ns
tsu3 Setup time, CSx valid before IOW↓ (see Note 2) 10 ns
tsu4 Setup time, A2 −A0 valid before IOW↓ (see Note 2) 15 ns
tsu5 Setup time, D7 −D0 valid before IOW↑10 ns
th3 Hold time, A2 −A0 valid after IOW↑ (see Note 2) 5 ns
th4 Hold time, CSx valid after IOW↑ (see Note 2) 5 ns
th5 Hold time, D7 −D0 valid after IOW↑25 ns
td3 Delay time, tsu4 + tw5 + td4 120 ns
td4 Delay time, IOW↑ to IOW or IOR↓55 ns
NOTE 2: The internal address strobe is always active.
read cycle switching characteristics over recommended ranges of operating free-air temperature
and supply voltage, CL = 100 pF (see Note 4 and Figure 4)
PARAMETER MIN MAX UNIT
ten Enable time, IOR↓ to D7− D0 valid 30 ns
tdis Disable time, IOR↑ to D7 −D0 released 0 20 ns
NOTE 4: VOL and VOH (and the external loading) determine the charge and discharge time.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
11
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
transmitter switching characteristics over recommended ranges of operating free-air temperature
and supply voltage (see Figures 6, 7, and 8)
PARAMETER TEST CONDITIONS MIN MAX UNIT
td5 Delay time, INTx↓ to TXx↓ at start See Note 7 8 24 RCLK
cycles
td6 Delay time, TXx↓ at start to INTx↑See Note 5 8 8 RCLK
cycles
td7 Delay time, IOW high or low (WR THR) to INTx↑See Note 5 16 32 RCLK
cycles
td8 Delay time, TXx↓ at start to TXRDY↓CL = 100 pF 8RCLK
cycles
tpd1 Propagation delay time, IOW (WR THR)↓ to INTx↓CL = 100 pF 35 ns
tpd2 Propagation delay time, IOR (RD IIR)↑ to INTx↓CL = 100 pF 30 ns
tpd3 Propagation delay time, IOW (WR THR)↑ to TXRDY↑CL = 100 pF 50 ns
NOTE 5: If the transmitter interrupt delay is active, this delay is lengthened by one character time minus the last stop-bit time.
receiver switching characteristics over recommended ranges of operating free-air temperature
and supply voltage (see Figures 9 through 13)
PARAMETER TEST CONDITIONS MIN MAX UNIT
td9 Delay time, stop bit to INTx↑ or stop bit to RXRDY↓ or read RBR to set interrupt See Note 6 1RCLK
cycle
tpd4 Propagation delay time, Read RBR/LSR to INTx↓/LSR interrupt↓CL = 100 pF,
See Note 7 40 ns
tpd5 Propagation delay time, IOR RCLK↓ to RXRDY↑See Note 7 30 ns
NOTES: 6. The receiver data available indicator, the overrun error indicator, the trigger level interrupts, and the active RXRDY indicator are
delayed three RCLK (internal receiver timing clock) cycles in the FIFO mode (FCR0 = 1). After the first byte has been received, status
indicators (PE, FE, BI) are delayed three RCLK cycles. These indicators are updated immediately for any further bytes received after
IOR goes active for a read from the RBR register. There are eight RCLK cycle delays for trigger change level interrupts.
7. RCLK and baudout are internal signals derived from divisor latches LSB (DLL) and MSB (DLM) and input clock.
modem control switching characteristics over recommended ranges of operating free-air
temperature and supply voltage, CL = 100 pF (see Figures 14, 15, 16, and 17)
PARAMETER MIN MAX UNIT
tpd6 Propagation delay time, IOW (WR MCR)↑ to RTSx, DTRx↑50 ns
tpd7 Propagation delay time, modem input CTSx, DSRx, and DCDx ↓↑ to INTx↑30 ns
tpd8 Propagation delay time, IOR (RD MSR)↑ to interrupt↓35 ns
tpd9 Propagation delay time, RIx↑ to INTx↑30 ns
tpd10 Propagation delay time, CTS low to SOUT↓(See Note 7) 24 baudout
cycles
tsu6 Setup time CTS high to midpoint of Tx stop bit 2baudout
cycles
tpd11 Propagation delay time, RCV threshold byte to RTS↑2baudout
cycles
tpd12 Propagation delay time, IOR (RD RBR) low (read of last byte in receive FIFO) to RTS↓2baudout
cycles
tpd13 Propagation delay time, first data bit of 16th character to RTS↑2baudout
cycles
tpd14 Propagation delay time, IOR (RD RBR) low to RTS↓2baudout
cycles
7. RCLK and baudout are internal signals derived from divisor latches LSB (DLL) and MSB (DLM) and input clock.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
12 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PARAMETER MEASUREMENT INFORMATION
Clock
(XTAL1)
fclock = 16 MHz MAX
tw2
tw1
0.8 V
2 V
tw3
RESET
2 V2 V
0.8 V 0.8 V
(a) CLOCK INPUT VOLTAGE WAVEFORM
(b) RESET VOLTAGE WAVEFORM
Figure 1. Clock Input and RESET Voltage Waveforms
82 pF
(see Note A)
680 Ω
2.54 V
Device Under Test
TL16C554
NOTE A: This includes scope and jig capacitance.
Figure 2. Output Load Circuit
9-Pin D Connector
Serial
Channel 1
Buffers
Serial
Channel 2
Buffers
Serial
Channel 3
Buffers
Serial
Channel 4
Buffers
9-Pin D Connector
9-Pin D Connector
9-Pin D Connector
Data Bus
Address Bus
Control Bus Quadruple
ACE
TL16C554A
Figure 3. Basic Test Configuration
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
13
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PARAMETER MEASUREMENT INFORMATION
tw4
td2
Active
Valid
A2, A1, A0
Valid
Valid Data
IOR
IOW
D7 − D0
th1
th2
tsu1
tsu2
Active
td1
ten tdis
or
Active
CSx
50%
50%
50%
50% 50%
50%
50%
50%
Figure 4. Read Cycle Timing Waveforms
Valid
A2, A1, A0
Valid
Valid Data
IOR
IOW
D7 − D0
tsu3
tsu4
tw5
td3
th4
td4
tsu5 th5
Active
or
Active
th3
Active
CSx
50%
50%
50%
50% 50%
50%
50%
50%
Figure 5. Write Cycle Timing Waveforms
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
14 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PARAMETER MEASUREMENT INFORMATION
Start
IOR
(RD IIR)
IOW
(
WR THR)
tpd1
td7
td5 td6
tpd2
Start
Data (5 −8)
Parity
Stop (1 −2)
tpd1
TXx
INTx
50%
50%
50% 50%50% 50%
50%
50%
50%
50%
50%
Figure 6. Transmitter Timing Waveforms
Byte #1
IOW
(WR THR)
Data
td8
StartParity Stop
tpd3
TXRDY
TXx
FIFO Empty
50%
50%
50%50%
Figure 7. Transmitter Ready Mode 0 Timing Waveforms
IOW
(WR THR)
TXRDY
Byte #16
Data
td8
StartParity Stop
tpd3
Start
FIFO Full
TXx
50%
50%
50%
50%
Figure 8. Transmitter Ready Mode 1 Timing Waveforms
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
15
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PARAMETER MEASUREMENT INFORMATION
tpd4
Parity StopStart Data Bits (5 −8)
TL16C450 Mode:
Sample Clock
SIN
(receiver input data)
INTx
(data ready or
RCVR ERR)
IOR
td9
Active
50% 50%
50%
Figure 9. Receiver Timing Waveforms
Start Data Bits (5 −8) Parity Stop
Sample
Clock
td9 tpd4
INTx (trigger
interrupt)
(FCR6, 7 = 0, 0)
(FIFO at or
above trigger
level)
(FIFO below
trigger level)
Active
IOR
(RD RBR)
IOR
(RD LSR)
tpd4
Active
RXx
LSR
Interrupt
50%50%
50%
50%50%
50%
Figure 10. Receiver FIFO First Byte (Sets RDR) Waveforms
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
16 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PARAMETER MEASUREMENT INFORMATION
Stop
td9 (see Note A)
tpd4
Top Byte of FIFO
tpd4
td9
Active Active
Sample
Clock
INTx
(time-out or
trigger level)
Interrupt
IOR
(RD RBR)
IOR
(RD LSR)
Previous BYTE
Read From FIFO
Active
(FIFO at or above
trigger level)
(FIFO below
trigger level)
RXx
INTx
Interrupt
50%50%
50%
50% 50%
50%
50%
NOTE A: This is the reading of the last byte in the FIFO.
Figure 11. Receiver FIFO After First Byte (After RDR Set) Waveforms
Active
(see Note A)
Stop
td9
(see Note B)
tpd5
IOR
(RD RBR)
Sample
Clock
RXRDY
RXx
50%
50%
50%
NOTES: A. This is the reading of the last byte in the FIFO.
B. If FCR0 = 1, then td9 = 3 RCLK cycles. For a time-out interrupt, td9 = 8 RCLK cycles.
Figure 12. Receiver Ready Mode 0 Timing Waveforms
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
17
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PARAMETER MEASUREMENT INFORMATION
Active
(see Note A)
Stop
td9
(see Note B)
tpd5
IOR
(RD RBR)
SIN
(first byte that reaches
the trigger level)
Sample
Clock
RXRDY 50%
50%
50%
NOTES: A. This is the reading of the last byte in the FIFO.
B. If FCR0 = 1, td9 = 3 RCLK cycles. For a trigger change level interrupt, td9 = 8 RCLK.
Figure 13. Receiver Ready Mode 1 Timing Waveforms
tpd6 tpd6
tpd7 tpd7
tpd8 tpd9
IOW
(WR MCR)
IOR
(RD MSR)
RTSx, DTRx
CTSx, DSRx,
DCDx
RIx
INTx
50%
50%
50%
50%
50%
50%
50%50% 50%
50%
50%
50%
Figure 14. Modem Control Timing Waveforms
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
18 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Midpoint of Stop Bit
tpd10
tsu6
CTS
TXx
50% 50%
50%
Figure 15. CTS and TX Autoflow Control Timing (Start and Stop) Waveforms
tPD12
RXx
50%
tPD11
50%
50%
Midpoint of Stop Bit
RTSx
RD RBR
IOR
Figure 16. Auto-RTS Timing for RCV Threshold of 1, 4, or 8 Waveforms
tpd14
RXx
50%
tpd13
50%
50%
Midpoint of Data Bit 0
RTSx
RD RBR
15th Character 16th Character
IOR
Figure 17. Auto-RTS Timing for RCV Threshold of 14 Waveforms
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
19
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
Three types of information are stored in the internal registers used in the ACE: control, status, and data. Mnemonic
abbreviations for the registers are shown in Table 1. Table 2 defines the address location of each register and whether
it is read only, write only, or read writable.
Table 1. Internal Register Mnemonic Abbreviations
CONTROL MNEMONIC STATUS MNEMONIC DATA MNEMONIC
Line-control register LCR Line-status register LSR Receiver-buffer register RBR
FIFO-control register FCR Modem-status register MSR Transmitter-holding register THR
Modem-control register MCR
Divisor-latch LSB DLL
Divisor-latch MSB DLM
Interrupt enable register IER
Table 2. Register Selection†
DLAB‡A2§A1§A0§READ MODE WRITE MODE
0 0 0 0 Receiver-buffer register Transmitter-holding register
0001 Interrupt-enable register
X0 1 0 Interrupt-identification register FIFO-control register
X011 Line-control register
X100 Modem-control register
X1 0 1 Line-status register
X1 1 0 Modem-status register
X1 1 1 Scratchpad register Scratchpad register
1000 LSB divisor-latch
1 0 0 1 MSB divisor-latch
X = irrelevant, 0 = low level, 1 = high level
†The serial channel is accessed when either CSA or CSD is low.
‡DLAB is the divisor-latch access bit, located in bit 7 of the LCR.
§A2 −A0 are device terminals.
Individual bits within the registers with the bit number in parenthesis are referred to by the register mnemonic. For
example, LCR7 refers to line-control register bit 7. The transmitter-buffer register and the receiver-buffer register are
data registers that hold from five to eight bits of data. If less than eight data bits are transmitted, data is right-justified
to the LSB. Bit 0 of a data word is always the first serial-data bit received and transmitted. The ACE data registers
are double buffered (TL16450 mode) or FIFO buffered (FIFO mode) so that read and write operations can be
performed when the ACE is performing the parallel-to-serial or serial-to-parallel conversion.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
20 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
accessible registers
The system programmer, using the CPU, has access to and control over any of the ACE registers that are
summarized in Table 1. These registers control ACE operations, receive data, and transmit data. Descriptions
of these registers follow Table 3.
Table 3. Summary of Accessible Registers
ADDRES REGISTER REGISTER ADDRESS
ADDRES
S
REGISTER
MNEMONIC BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
0 RBR
(read only)
Data Bit 7
(MSB)
Data Bit 6 Data Bit 5 Data
Bit 4
Data Bit 3 Data Bit 2 Data Bit 1 Data Bit 0
(LSB)
0 THR
(write only)
Data BIt 7 Data BIt 6 Data BIt 5 Data
BIt 4
Data BIt 3 Data BIt 2 Data BIt 1 Data BIt 0
0†DLL Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
1†DLM Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8
1 IER 0 0 0 0 (EDSSI)
Enable
modem
status
interrupt
(ERLSI)
Enable
receiver
line status
interrupt
(ETBEI)
Enable
transmitter
holding
register empty
interrupt
(ERBI)
Enable
received
data
available
interrupt
2 FCR
(write only)
Receiver
Trigger
(MSB)
Receiver
Trigger
(LSB)
Reserved Reserved DMA
mode
select
Transmit
FIFO reset
Receiver
FIFO reset
FIFO Enable
2 IIR
(read only)
FIFOs
Enabled‡
FIFOs
Enabled‡
0 0 Interrupt
ID Bit (3)‡
Interrupt ID
Bit (2)
Interrupt ID
Bit (1)
0 If interrupt
pending
3 LCR (DLAB)
Divisor
latch
access bit
Set break Stick parity (EPS)
Even-
parity
select
(PEN)
Parity
enable
(STB)
Number of
stop bits
(WLSB1)
Word-length
select bit 1
(WLSB0)
Word-length
select bit 0
4 MCR 0 0 Autoflow
control
enable
(AFE)
Loop OUT2
Enable
external
interrupt
(INT)
Reserved (RTS)
Request to
send
(DTR) Data
terminal
ready
5 LSR Error in
receiver
FIFO‡
(TEMT)
Transmitter
registers
empty
(THRE)
Transmitter
holding
register
empty
(BI)
Break
interrupt
(FE)
Framing
error
(PE)
Parity error
(OE)
Overrun error
(DR)
Data ready
6 MSR (DCD)
Data
carrier
detect
(RI)
Ring
indicator
(DSR)
Data set
ready
(CTS)
Clear to
send
(ΔDCD)
Delta data
carrier
detect
(TERI)
Trailing
edge ring
indicator
(ΔDSR)
Delta data
set ready
(ΔCTS)
Delta
clear to send
7 SCR Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
†DLAB = 1
‡These bits are always 0 when FIFOs are disabled.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
21
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
FIFO-control register (FCR)
The FCR is a write-only register at the same location as the IIR. It enables the FIFOs, sets the trigger level of
the receiver FIFO, and selects the type of DMA signalling.
DBit 0: FCR0 enables the transmit and receive FIFOs. All bytes in both FIFOs can be cleared by clearing
FCR0. Data is cleared automatically from the FIFOs when changing from the FIFO mode to the TL16C450
mode (see FCR bit 0) and vice versa. Programming of other FCR bits is enabled by setting FCR0.
DBit 1: When set, FCR1 clears all bytes in the receiver FIFO and resets its counter. This does not clear the
shift register.
DBit 2: When set, FCR2 clears all bytes in the transmit FIFO and resets the counter. This does not clear the
shift register.
DBit 3: When set, FCR3 changes RXRDY and TXRDY from mode 0 to mode 1 if FCR0 is set.
DBits 4 and 5: FCR4 and FCR5 are reserved for future use.
DBits 6 and 7: FCR6 and FCR7 set the trigger level for the receiver FIFO interrupt and the auto-RTS flow
control (see Table 4).
Table 4. Receiver FIFO Trigger Level
BIT RECEIVER FIFO
7 6
RECEIVER
FIFO
TRIGGER LEVEL (BYTES)
0 0 01
0 1 04
1 0 08
1 1 14
FIFO interrupt mode operation
The following receiver status occurs when the receiver FIFO and the receiver interrupts are enabled:
1. LSR0 is set when a character is transferred from the shift register to the receiver FIFO. When the FIFO is
empty, it is reset.
2. IIR = 06 receiver line status interrupt has higher priority than the receive data available interrupt
IIR = 04.
3. Receive data available interrupt is issued to the CPU when the programmed trigger level is reached by the
FIFO. As soon as the FIFO drops below its programmed trigger level, it is cleared.
4. IIR = 04 (receive data available indicator) also occurs when the FIFO reaches its trigger level. It is cleared
when the FIFO drops below the programmed trigger level.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
22 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
FIFO interrupt mode operation (continued)
The following receiver FIFO character time-out status occurs when receiver FIFO and the receiver interrupts
are enabled.
1. When the following conditions exist, a FIFO character time-out interrupt occurs:
a. Minimum of one character in FIFO
b. No new serial characters have been received for at least four character times. At 300 baud and 12-bit
characters, the FIFO time-out interrupt causes a latency of 160 ms maximum from received character
to interrupt generation.
c. The receive FIFO has not been read for at least four character times.
2. By using the XTAL1 input for a clock signal, the character times can be calculated. The delay is proportional
to the baud rate.
3. The time-out timer is reset after the CPU reads the receiver FIFO or after a new character is received. This
occurs when there has been no time-out interrupt.
4. A time-out interrupt is cleared and the timer is reset when the CPU reads a character from the receiver FIFO.
Transmit interrupts occurs as follows when the transmitter and transmit FIFO interrupts are enabled
(FCR0 =1, IER1 = 1).
1. When the transmitter FIFO is empty, the transmitter holding register interrupt (IIR = 02) occurs. The interrupt
is cleared when the transmitter holding register is written to or the IIR is read. One to sixteen characters can
be written to the transmit FIFO when servicing this interrupt.
2. The transmitter FIFO empty indicators are delayed one character time minus the last stop-bit time whenever
the following occurs:
THRE = 1, and there have not been at least two bytes in transmit FIFO since the last THRE = 1. The first
transmitter interrupt comes immediately after changing FCR0, assuming the interrupt is enabled.
Receiver FIFO trigger level and character time-out interrupts have the same priority as the receive data
available interrupt. The transmitter holding register empty interrupt has the same priority as the transmitter FIFO
empty interrupt.
FIFO polled mode operation
When the FIFOs are enabled and all interrupts are disabled, the device is in the FIFO polled mode.
In the FIFO polled mode, there is no time-out condition indicated or trigger level reached. However, the receive
and transmit FIFOs still have the capability of holding characters. The LSR must be read to determine the ACE
status.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
23
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
interrupt-enable register (IER)
The IER independently enables the four serial channel interrupt sources that activate the interrupt (INTA, B, C,
D) output. All interrupts are disabled by clearing IER0 − IER3 of the IER. Interrupts are enabled by setting the
appropriate bits of the IER. Disabling the interrupt system inhibits the IIR and the active (high) interrupt output.
All other system functions operate in their normal manner, including the setting of the LSR and MSR. The
contents of the IER are shown in Table 3 and described in the following bulleted list:
DBit 0: When IER0 is set, IER0 enables the received data available interrupt and the timeout interrupts in
the FIFO mode.
DBit 1: When IER1 is set, the transmitter holding register empty interrupt is enabled.
DBit 2: When IER2 is set, the receiver line status interrupt is enabled.
DBit 3: When IER3 is set, the modem-status interrupt is enabled.
DBits 4 − 7: IER4 − IER7. These four bits of the IER are cleared.
interrupt-identification register (IIR)
In order to minimize software overhead during data character transfers, the serial channel prioritizes interrupts
into four levels as follows:
DPriority 1 − Receiver line status (highest priority)
DPriority 2 − Receiver data ready or receiver character timeout
DPriority 3 −Transmitter holding register empty
DPriority 4−Modem status (lowest priority)
The IIR stores information indicating that a prioritized interrupt is pending and the type of interrupt. The IIR
indicates the highest priority interrupt pending. The contents of the IIR are indicated in Table 5.
Table 5. Interrupt Control Functions
INTERRUPT
IDENTIFICATION
REGISTER
INTERRUPT SET AND RESET FUNCTIONS
BIT 3 BIT 2 BIT 1 BIT 0 PRIORITY
LEVEL INTERRUPT TYPE INTERRUPT SOURCE INTERRUPT
RESET CONTROL
0 0 0 1 — None None —
0 1 1 0 First Receiver line status OE, PE, FE, or BI LSR read
0 1 0 0 Second Received data available Receiver data available or
trigger level reached
RBR read until FIFO
drops below the trigger
level
1 1 0 0 Second Character time-out
indicator
No characters have been
removed from or input to the
receiver FIFO during the last
four character times, and there
is at least one character in it
during this time.
RBR read
0 0 1 0 Third THRE THRE IIR read (if THRE is the
interrupt source), or
THR write
0 0 0 0 Fourth Modem status CTS, DSR, RI, or DCD MSR read
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
24 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
interrupt-identification register (IIR) (continued)
DBit 0: IIR0 indicates whether an interrupt is pending. When IIR0 is cleared, an interrupt is pending.
DBits 1 and 2: IIR1 and IIR2 identify the highest priority interrupt pending as indicated in Table 5.
DBit 3: IIR3 is always cleared in the TL16C450 mode. This bit, along with bit 2, is set when in the FIFO mode
and a character time-out interrupt is pending.
DBits 4 and 5: IIR4 and IIR5 are always cleared.
DBits 6 and 7: IIR6 and IIR7 are set when FCR0 = 1.
line-control register (LCR)
The format of the data character is controlled by LCR. LCR may be read. Its contents are described in the
following bulleted list and shown in Figure 18.
DBits 0 and 1: LCR0 and LCR1 are word-length select bits. These bits program the number of bits in each
serial character and are shown in Figure 18.
DBit 2: LCR2 is the stop-bit select bit. This bit specifies the number of stop bits in each transmitted character.
The receiver always checks for one stop bit.
DBit 3: LCR3 is the parity-enable bit. When LCR3 is set, a parity bit between the last data word bit and the
stop bit is generated and checked.
DBit 4: LCR4 is the even-parity select bit. When this bit is set and parity is enabled (LCR3 is set), even parity
is selected. When this bit is cleared and parity is enabled, odd parity is selected.
DBit 5: LCR5 is the stick-parity bit. When parity is enabled (LCR3 is set) and this bit is set, the transmission
and reception of a parity bit is placed in the opposite state from the value of LCR4. This forces parity to a
known state and allows the receiver to check the parity bit in a known state.
DBit 6: LCR6 is a break-control bit. When this bit is set, the serial outputs TXx are forced to the spacing state
(low). The break-control bit acts only on the serial output and does not affect the transmitter logic. If the
following sequence is used, no invalid characters are transmitted because of the break.
Step 1. Load a zero byte in response to the transmitter holding register empty (THRE) status indicator.
Step 2. Set the break in response to the next THRE status indicator.
Step 3. Wait for the transmitter to be idle when transmitter empty status signal is set (TEMT = 1); then
clear the break when the normal transmission has to be restored.
DBit 7: LCR7 is the divisor-latch access bit (DLAB) bit. This bit must be set to access the divisor latches DLL
and DLM of the baud-rate generator during a read or write operation. LCR7 must be cleared to access the
receiver-buffer register, the transmitter-holding register, or the interrupt-enable register.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
25
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
line-control register (LCR) (continued)
Word-Length
Select
0 0 = 5 Data Bits
0 1 = 6 Data Bits
1 0 = 7 Data Bits
1 1 = 8 Data bits
LINE CONTROL REGISTER
LCR
7
LCR
6
LCR
5
LCR
4
LCR
3
LCR
2
LCR
1
LCR
0
Stop-Bit
Select
0 = 1 Stop Bit
1 = 1.5 Stop Bits if 5 Data Bits Selected
2 Stop Bits if 6, 7, 8 Data Bits Selected
Parity Enable 0 = Parity Disabled
1 = Parity Enabled
Even-Parity
Select
0 = Odd Parity
1 = Even Parity
Stick Parity 0 = Stick Parity Disabled
1 = Stick Parity Enabled
Break Control 0 = Break Disabled
1 = Break Enabled
Divisor-Latch
Access BIt
0 = Access Receiver Buffer
1 = Access Divisor Latches
Figure 18. Line-Control Register Contents
line-status register (LSR)
The LSR is a single register that provides status indicators. The LSR shown in Table 6 is described in the
following bulleted list:
DBit 0: LSR0 is the data ready (DR) bit. Data ready is set when an incoming character is received and
transferred to the receiver-buffer register or to the FIFO. LSR0 is cleared by a CPU read of the data in the
receiver-buffer register or in the FIFO.
DBit 1: LSR1 is the overrun error (OE) bit. An overrun error indicates that data in the receiver-buffer register
is not read by the CPU before the next character is transferred to the receiver-buffer register, therefore
overwriting the previous character. The OE indicator is cleared whenever the CPU reads the contents of
the LSR. An overrun error occurs in the FIFO mode after the FIFO is full and the next character is completely
received. The overrun error is detected by the CPU on the first LSR read after it occurs. The character in
the shift register is not transferred to the FIFO, but it is overwritten.
DBit 2: LSR2 is the parity error (PE) bit. A parity error indicates that the received data character does not
have the correct parity as selected by LCR3 and LCR4. The PE bit is set upon detection of a parity error
and is cleared when the CPU reads the contents of the LSR. In the FIFO mode, the parity error is associated
with a particular character in the FIFO. LSR2 reflects the error when the character is at the top of the FIFO.
DBit 3: LSR3 is the framing error (FE) bit. A framing error indicates that the received character does not have
a valid stop bit. LSR3 is set when the stop bit following the last data bit or parity bit is detected as a zero
bit (spacing level). The FE indicator is cleared when the CPU reads the contents of the LSR. In the FIFO
mode, the framing error is associated with a particular character in the FIFO. LSR3 reflects the error when
the character is at the top of the FIFO.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
26 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
line-status register (LSR) (continued)
DBit 4: LSR4 is the break interrupt (BI) bit. Break interrupt is set when the received data input is held in the
spacing (low) state for longer than a full word transmission time (start bit + data bits + parity + stop bits).
The BI indicator is cleared when the CPU reads the contents of the LSR. In the FIFO mode, this is associated
with a particular character in the FIFO. LSR2 reflects the BI when the break character is at the top of the
FIFO. The error is detected by the CPU when its associated character is at the top of the FIFO during the
first LSR read. Only one zero character is loaded into the FIFO when BI occurs.
LSR1 − LSR4 are the error conditions that produce a receiver line status interrupt (priority 1 interrupt in the
interrupt-identification register) when any of the conditions are detected. This interrupt is enabled by setting
IER2 in the interrupt-enable register.
DBit 5: LSR5 is the transmitter holding register empty (THRE) bit. THRE indicates that the ACE is ready to
accept a new character for transmission. The THRE bit is set when a character is transferred from the
transmitter holding register (THR) to the transmitter shift register (TSR). LSR5 is cleared when the CPU
loads THR. LSR5 is not cleared by a CPU read of the LSR. In the FIFO mode, this bit is set when the transmit
FIFO is empty, and it is cleared when one byte is written to the transmit FIFO. When the THRE interrupt
is enabled by IER1, THRE causes a priority 3 interrupt in the IIR. If THRE is the interrupt source indicated
by IIR, INTRPT is cleared by a read of the IIR.
DBit 6: LSR6 is the transmitter register empty (TEMT) bit. TEMT is set when both THR and TSR are empty.
LSR6 is cleared when a character is loaded into THR, and remains low until the character is transferred out
of TXx. TEMT is not cleared by a CPU read of the LSR. In the FIFO mode, this bit is set when both the
transmitter FIFO and shift register are empty.
DBit 7: LSR7 is the receiver FIFO error bit. The LSR7 bit is cleared in the TL16C450 mode (see FCR bit 0).
In the FIFO mode, it is set when at least one of the following data errors is in the FIFO: parity error, framing
error, or break interrupt indicator. It is cleared when the CPU reads the LSR, unless there are subsequent
errors in the FIFO.
NOTE
The LSR may be written. However, this function is intended only for factory test. It should be considered as read
only by applications software.
Table 6. Line-Status Register BIts
LSR BITS 1 0
LSR0 data ready (DR) Ready Not ready
LSR1 overrun error (OE) Error No error
LSR2 parity error (PE) Error No error
LSR3 framing error (FE) Error No error
LSR4 break interrupt (BI) Break No break
LSR5 transmitter holding register empty (THRE) Empty Not empty
LSR6 transmitter register empty (TEMT) Empty Not empty
LSR7 receiver FIFO error Error in FIFO No error in FIFO
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
27
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
modem-control register (MCR)
The MCR controls the interface with the modem or data set as described in Figure 19. The MCR can be written
and read. Outputs RTS and DTR are directly controlled by their control bits in this register. A high input asserts
a low signal (active) at the output terminals. MCR bits 0, 1, 2, 3, and 4 are shown as follows:
DBit 0: When MCR0 is set, the DTR output is forced low. When MCR0 is cleared, the DTR output is forced
high. The DTR output of the serial channel may be input into an inverting line driver in order to obtain the
proper polarity input at the modem or data set.
DBit1: When MCR1 is set, the RTS output is forced low. When MCR1 is cleared, the RTS output is forced
high. The RTS output of the serial channel may be input into an inverting line driver to obtain the proper
polarity input at the modem or data set.
DBit 2: MCR2 has no effect on operation.
DBit 3: When MCR3 is set, the external serial channel interrupt is enabled.
DBit 4: MCR4 provides a local loopback feature for diagnostic testing of the channel. When MCR4 is set,
serial output TXx is set to the marking (high) state and SIN is disconnected. The output of the TSR is looped
back into the RSR input. The four modem control inputs (CTS, DSR, DCD, and RI) are disconnected. The
four modem control output bits (DTR, RTS, OUT1, and OUT2) are internally connected to the four modem
control input bits (DSR, CTS, RI, and DCD), respectively. The modem control output terminals are forced
to their inactive (high) state. In the diagnostic mode, data transmitted is received by its own receiver. This
allows the processor to verify the transmit and receive data paths of the selected serial channel. Interrupt
control is fully operational; however, modem-status interrupts are generated by controlling the lower four
MCR bits internally. Interrupts are not generated by activity on the external terminals represented by those
four bits.
DBit 5: This bit is the autoflow control enable (AFE). When set, the autoflow control is enabled, as described
in the detailed description.
The ACE flow control can be configured by programming bits 1 and 5 of the MCR, as shown in Table 7.
Table 7. ACE Flow Configuration
MSR BIT 5
(AFE)
MSR BIT 1
(RTS)
ACE FLOW CONFIGURATION
1 1 Auto-RTS and auto-CTS enabled (autoflow control enabled)
1 0 Auto-CTS only enabled
0 X Auto-RTS and auto-CTS disabled
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
28 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
modem-control register (MCR) (continued)
DBit 6 − Bit 7: MCR5, MCR6, and MCR7 are permanently cleared.
Data Terminal
Ready
0 = DTR Output Inactive (high)
1 = DTR Output Active (low)
MODEM CONTROL REGISTER
MCR
7
MCR
6
MCR
5
MCR
4
MCR
3
MCR
2
Loop 0 = Loop Disabled
1 = Loop Enabled
Bits Are Set to Logic 0
Request
to Send
0 = RTS Output Inactive (high)
1 = RTS Output Active (low)
MCR
1
MCR
0
Out1 (internal)
Out2 (internal)
No effect on external operation
0 = External Interrupt Disabled
1 = External Interrupt Enabled
AFE 0 = AFE Disabled
1 = AFE Enabled
Figure 19. Modem-Control Register Contents
modem-status register (MSR)
The MSR provides the CPU with status of the modem input lines for the modem or peripheral devices. The MSR
allows the CPU to read the serial channel modem signal inputs by accessing the data bus interface of the ACE.
It also reads the current status of four bits of the MSR that indicate whether the modem inputs have changed
since the last reading of the MSR. The delta status bits are set when a control input from the modem changes
states, and are cleared when the CPU reads the MSR.
The modem input lines are CTS, DSR, RI, and DCD. MSR4 − MSR7 are status indicators of these lines. A status
bit = 1 indicates the input is low. When the status bit is cleared, the input is high. When the modem-status
interrupt in the IER is enabled (IIR3 is set), an interrupt is generated whenever any one of MSR0 − MSR3 is set,
except as noted below in the delta CTS description. The MSR is a priority 4 interrupt. The contents of the MSR
are described in Table 8.
DBit 0: MSR0 is the delta clear-to-send (ΔCTS) bit. ΔCTS indicates that the CTS input to the serial channel
has changed state since it was last read by the CPU. No interrupt will be generated if auto-CTS mode is
enabled.
DBit 1: MSR1 is the delta data set ready (ΔDSR) bit. ΔDSR indicates that the DSR input to the serial channel
has changed states since the last time it was read by the CPU.
DBit 2: MSR2 is the trailing edge of ring indicator (TERI) bit. TERI indicates that the RI input to the serial
channel has changed states from low to high since the last time it was read by the CPU. High-to-low
transitions on RI do not activate TERI.
DBit 3: MSR3 is the delta data carrier detect (ΔDCD) bit. ΔDCD indicates that the DCD input to the serial
channel has changed states since the last time it was read by the CPU.
DBit 4: MSR4 is the clear-to-send (CTS) bit. CTS is the complement of the CTS input from the modem
indicating to the serial channel that the modem is ready to receive data from SOUT. When the serial channel
is in the loop mode (MCR4 = 1), MSR4 reflects the value of RTS in the MCR.
DBit 5: MSR5 is the data set ready DSR bit. DSR is the complement of the DSR input from the modem to
the serial channel that indicates that the modem is ready to provide received data from the serial channel
receiver circuitry. When the channel is in the loop mode (MCR4 is set), MSR5 reflects the value of DTR in
the MCR.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
29
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
modem-status register (MSR) (continued)
DBit 6: MSR6 is the ring indicator (RI) bit. RI is the complement of the RIx inputs. When the channel is in the
loop mode (MCR4 is set), MSR6 reflects the value of OUT1 in the MCR.
DBit 7: MSR7 is the data carrier detect (DCD) bit. Data carrier detect indicates the status of the data carrier
detect (DCD) input. When the channel is in the loop mode (MCR4 is set), MSR7 reflects the value of OUT2
in the MCR.
Reading the MSR clears the delta modem status indicators but has no effect on the other status bits. For LSR
and MSR, the setting of status bits is inhibited during status register read operations. If a status condition is
generated during a read IOR operation, the status bit is not set until the trailing edge of the read. When a status
bit is set during a read operation and the same status condition occurs, that status bit is cleared at the trailing
edge of the read instead of being set again. In the loopback mode, CTS, DSR, RI, and DCD inputs are ignored
when modem-status interrupts are enabled; however, a modem-status interrupt can still be generated by writing
to MCR3−MCR0. Applications software should not write to the MSR.
Table 8. Modem-Status Register BIts
MSR BIT MNEMONIC DESCRIPTION
MSR0 ΔCTS Delta clear to send
MSR1 ΔDSR Delta data set ready
MSR2 TERI Trailing edge of ring indicator
MSR3 ΔDCD Delta data carrier detect
MSR4 CTS Clear to send
MSR5 DSR Data set ready
MSR6 RI Ring indicator
MSR7 DCD Data carrier detect
programming
The serial channel of the ACE is programmed by control registers LCR, IER, DLL, DLM, MCR, and FCR. These
control words define the character length, number of stop bits, parity, baud rate, and modem interface.
While the control registers can be written in any order, the IER should be written last because it controls the
interrupt enables. Once the serial channel is programmed and operational, these registers can be updated any
time the ACE serial channel is not transmitting or receiving data.
programmable baud-rate generator
The ACE serial channel contains a programmable baud-rate generator (BRG) that divides the clock (dc to
8 MHz) by any divisor from 1 to 216 −1. Two 8-bit divisor-latch registers store the divisor in a 16-bit binary format.
These divisor-latch registers must be loaded during initialization. A 16-bit baud counter is immediately loaded
upon loading of either of the divisor latches. This prevents long counts on initial load. The BRG can use any of
three different popular frequencies to provide standard baud rates. These frequencies are 1.8432 MHz,
3.072 MHz, 8 MHz, and 16 MHz. With these frequencies, standard bit rates from 50 kbps to 512 kbps are
available. Tables 9, 10, 11, and 12 illustrate the divisors needed to obtain standard rates using these three
frequencies. The output frequency of the baud-rate generator is 16 times the data rate [divisor # = clock + (baud
rate × 16)]. RCLK runs at this frequency.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
30 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
programmable baud-rate generator (continued)
Table 9. Baud Rates Using a 1.8432-MHz Crystal
BAUD RATE
DESIRED
DIVISOR (N) USED TO
GENERATE 16 × CLOCK
PERCENT ERROR DIFFERENCE
BETWEEN DESIRED AND ACTUAL
50 2304 —
75 1536 —
110 1047 0.026
134.5 857 0.058
150 768 —
300 384 —
600 192 —
1200 96 —
1800 64 —
2000 58 0.690
2400 48 —
3600 32 —
4800 24 —
7200 16 —
9600 12 —
19200 6 —
38400 3 —
56000 2 2.860
Table 10. Baud Rates Using a 3.072-MHz Crystal
BAUD RATE
DESIRED
DIVISOR (N) USED TO
GENERATE 16 × CLOCK
PERCENT ERROR DIFFERENCE
BETWEEN DESIRED AND ACTUAL
50 3840 —
75 2560 —
110 1745 0.026
134.5 1428 0.034
150 1280 —
300 640 —
600 320 —
1200 160 —
1800 107 0.312
2000 96 —
2400 80 —
3600 53 0.628
4800 40 —
7200 27 1.230
9600 20 —
19200 10 —
38400 5 —
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
31
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
programmable baud-rate generator (continued)
Table 11. Baud Rates Using an 8-MHz Clock
BAUD RATE
DESIRED
DIVISOR (N) USED TO
GENERATE 16 × CLOCK
PERCENT ERROR DIFFERENCE
BETWEEN DESIRED AND ACTUAL
50 10000 —
75 6667 0.005
110 4545 0.010
134.5 3717 0.013
150 333 0.010
300 1667 0.020
600 883 0.040
1200 417 0.080
1800 277 0.080
2000 250 —
2400 208 0.160
3600 139 0.080
4800 104 0.160
7200 69 0.644
9600 52 0.160
19200 26 0.160
38400 13 0.160
56000 9 0.790
128000 4 2.344
256000 2 2.344
512000 1 2.400
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
32 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Table 12. Baud Rates Using an 16-MHz Clock
BAUD RATE
DESIRED
DIVISOR (N) USED TO
GENERATE 16 × CLOCK
PERCENT ERROR DIFFERENCE
BETWEEN DESIRED AND ACTUAL
50 20000 0
75 13334 0.00
110 9090 0.01
134.5 7434 0.01
150 6666 0.01
300 3334 −0.02
600 1666 0.04
1200 834 −0.08
1800 554 0.28
2000 500 0.00
2400 416 0.16
3600 278 −0.08
4800 208 0.16
7200 138 0.64
9600 104 0.16
19200 52 0.16
38400 26 0.16
56000 18 −0.79
128000 8 −2.34
256000 4 −2.34
512000 2 −2.34
1000000 1 0.00
receiver
Serial asynchronous data is input into the RXx terminal. The ACE continually searches for a high-to-low
transition. When the transition is detected, a circuit is enabled to sample incoming data bits at the optimum point,
which is the center of each bit. The start bit is valid when RXx is still low at the sample point. Verifying the start
bits prevents the receiver from assembling a false data character due to a low-going noise spike on the RXx
input.
The number of data bits in a character is controlled by LCR0 and LCR1. Parity checking, generation, and polarity
are controlled by LCR3 and LCR4. Receiver status is provided in the LSR. When a full character is received,
including parity and stop bits, the data received indicator in LSR0 is set. In non-FIFO mode, the CPU reads the
RBR, which clears LSR0. If the character is not read prior to a new character transfer from RSR to RBR, an
overrun occurs and the overrun error status indicator is set in LSR1. If there is a parity error, the parity error is
set in LSR2. If a stop bit is not detected, a framing error indicator is set in LSR3.
In the FIFO mode, the data character and the associated error bits are stored in the receiver FIFO. If the data
in RXx is a symmetrical square wave, the center of the data cells occurs within ±3.125% of the actual center,
providing an error margin of 46.875%. The start bit can begin as much as one 16× clock cycles prior to being
detected.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
33
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
autoflow control (see Figure 20)
Autoflow control is comprised of auto-CTS and auto-RTS. With auto-CTS, the CTS input must be active before
the transmitter FIFO can send data. With auto-RTS, RTS becomes active when the receiver can handle more
data and notifies the sending serial device. When RTS is connected to CTS, data transmission does not occur
unless the receiver FIFO has space for the data; thus, overrun errors are eliminated using ACE1 and ACE2 from
a TL16C554A with the autoflow control enabled. Otherwise, overrun errors may occur when the transmit-data
rate exceeds the receiver FIFO read latency.
RCV
FIFO
Serial to
Parallel
Flow
Control
XMT
FIFO
Parallel
to Serial
Flow
Control
Parallel
to Serial
Flow
Control
Serial to
Parallel
Flow
Control
XMT
FIFO
RCV
FIFO
ACE1 ACE2
D7 − D0
SIN SOUT
RTS CTS
SOUT SIN
CTS RTS
D7 − D0
Figure 20. Autoflow Control (Auto-RTS and Auto-CTS) Example
auto-RTS (see Figure 20)
Auto-RTS data flow control originates in the receiver timing and control block (see functional block diagram)
and is linked to the programmed receiver FIFO trigger level. When the receiver FIFO level reaches a trigger level
of 1, 4, or 8 (see Figure 22) RTS is deasserted. With trigger levels of 1, 4, and 8, the sending ACE may send
an additional byte after the trigger level is reached (assuming the sending ACE has another byte to send)
because it may not recognize the deassertion of RTS until after it has begun sending the additional byte. RTS
is automatically reasserted once the RCV FIFO is emptied by reading the receiver-buffer register.
When the trigger level is 14 (see Figure 23), RTS is deasserted after the first data bit of the 16th character is
present on the SIN line. RTS is reasserted when the RCV FIFO has at least one available byte space.
auto-CTS (see Figure 20)
The transmitter circuitry checks CTS before sending the next data byte. When CTS is active, it sends the next
byte. To stop the transmitter from sending the following byte, CTS must be released before the middle of the
last stop bit currently being sent (see Figure 21). The auto-CTS function reduces interrupts to the host system.
When flow control is enabled, CTS level changes do not trigger host interrupts because the device automatically
controls its own transmitter. Without auto-CTS the transmitter sends any data present in the transmit FIFO and
a receiver overrun error may result.
enabling autoflow control and auto-CTS
Autoflow control is enabled by setting modem-control register bits 5 (autoflow enable or AFE) and 1 (RTS) to
a 1. Autoflow incorporates both auto-RTS and auto-CTS. When only auto-CTS is desired, bit 1 in the modem-
control register should be cleared (this assumes that an external control signal is driving CTS).
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
34 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
auto-CTS and auto-RTS functional timing
Start Bits 0 −7 Start Bits 0− 7 Start Bits 0 −7
Stop Stop Stop
SOUT
CTS
NOTES: A. When CTS is low, the transmitter keeps sending serial data out.
B. If CTS goes high before the middle of the last stop bit of the current byte, the transmitter finishes sending the current byte but it does
not send the next byte.
C. When CTS goes from high to low, the transmitter begins sending data again.
Figure 21. CTS Functional Timing Waveforms
The receiver FIFO trigger level can be set to 1, 4, 8, or 14 bytes. These are described in Figures 3 and 4.
Start Byte N Start Byte N+1 Start Byte
Stop Stop Stop
SIN
RTS
RD
(RD RBR) 12 N N+1
NOTES: A. N = RCV FIFO trigger level (1, 4, or 8 bytes)
B. The two blocks in dashed lines cover the case where an additional byte is sent as described in the preceding auto-RTS section.
Figure 22. RTS Functional Timing Waveforms, RCV FIFO Trigger Level = 1, 4, or 8 Bytes
Byte 14 Byte 15
SIN
RTS
RD
(RD RBR)
Start Byte 18 StopStart Byte 16 Stop
RTS Released After the
First Data Bit of Byte 16
NOTES: A. RTS is deasserted when the receiver receives the first data bit of the sixteenth byte. The receive FIFO is full after finishing the
sixteenth byte.
B. RTS is asserted again when there is at least one byte of space available and no incoming byte is in processing or there is more than
one byte of space available.
C. When the receive FIFO is full, the first receive buffer register read reasserts RTS.
Figure 23. RTS Functional Timing Waveforms, RCV FIFO Trigger Level = 14 Bytes
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
35
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
reset
After power up, the ACE RESET input should be held high for one microsecond to reset the ACE circuits to an
idle mode until initialization. A high on RESET causes the following:
1. Initializes the transmitter and receiver internal clock counters.
2. Clears the LSR, except for transmitter register empty (TEMT) and transmit holding register empty (THRE),
which are set. The MCR is also cleared. All of the discrete lines, memory elements, and miscellaneous logic
associated with these register bits are also cleared or turned off. The LCR, divisor latches, RBR, and
transmitter-buffer register are not affected.
RXRDY operation
In mode 0, RXRDY is asserted (low) when the receive FIFO is not empty; it is released (high) when the FIFO
is empty. In this way, the receiver FIFO is read when RXRDY is asserted (low).
In mode 1, RXRDY is asserted (low) when the receive FIFO has filled to the trigger level or a character time-out
has occurred (four character times with no transmission of characters); it is released (high) when the FIFO is
empty. In this mode, many received characters are read by the DMA device, reducing the number of times it
is interrupted.
RXRDY and TXRDY outputs from each of the four internal ACEs of the TL16C554A are ANDed together
internally. This combined signal is brought out externally to RXRDY and TXRDY.
Following the removal of the reset condition (RESET low), the ACE remains in the idle mode until programmed.
A hardware reset of the ACE sets the THRE and TEMT status bits in the LSR. When interrupts are subsequently
enabled, an interrupt occurs due to THRE. A summary of the effect of a reset on the ACE is given in Table 13.
Table 13. RESET Effects on Registers and Signals
REGISTER/SIGNAL RESET CONTROL RESET STATE
Interrupt-enable register Reset All bits cleared (0 −3 forced and 4 −7 permanent)
Interrupt-identification register Reset Bit 0 is set, bits 1, 2, 3, 6, and 7 are cleared,
Bits 4 −5 are permanently cleared
Line-control register Reset All bits cleared
Modem-control register Reset All bits cleared (5 −7 permanent)
FIFO-control register Reset All bits cleared
Line-status register Reset All bits cleared, except bits 5 and 6 are set
Modem-status register Reset Bits 0 −3 cleared, bits 4 −7 input signals
TXx Reset High
Interrupt (RCVR ERRS) Read LSR/reset Low
Interrupt (receiver data ready) Read RBR/reset Low
Interrupt (THRE) Read IIR/write THR/reset Low
Interrupt (modem status changes) Read MSR/reset Low
RTS Reset High
DTR Reset High
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
36 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
scratchpad register
The scratchpad register is an 8-bit read/write register that has no effect on any ACE channel. It is intended to
be used by the programmer to hold data temporarily.
TXRDY operation
In mode 0, TXRDY is asserted (low) when the transmit FIFO is empty; it is released (high) when the FIFO
contains at least one byte. In this way, the FIFO is written with 16 bytes when TXRDY is asserted (low).
In mode 1, TXRDY is asserted (low) when the transmit FIFO is not full; in this mode, the transmit FIFO is written
with another byte when TXRDY is asserted (low).
Driver
Optional
Driver
External
Clock
Optional
Clock
Output
Oscillator Clock
to Baud
Generator Logic
VCC
Crystal
Oscillator Clock
to Baud
Generator Logic
RX2
VCC
C1
RP
C2
XTAL1 XTAL1
XTAL2 XTAL2
TYPICAL CRYSTAL OSCILLATOR NETWORK
CRYSTAL RPRX2 C1 C2
3.1 MHz 1 MΩ1.5 kΩ10−30 pF 40−60 pF
1.8 MHz 1 MΩ1.5 kΩ10 −30 pF 40 −60 pF
Figure 24. Typical Clock Circuits
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
37
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Revision History
DATE REV PAGE SECTION DESCRIPTION
02 JUNE 2010 E 7 terminal functions table Added pin numbers to PN package
23 FEB 2010 C 37 48-pin PM package drawing and terminal function descriptions were added for
the new TL16C554APM device
25 AUG 2005 B 1 features Added voltage information to Up to 16−MHZ Clock Rate ....
29 JUL 2003 AChanges unknown
01 AUG 2001 *Original version
NOTE:Page numbers for previous revisions may differ from page numbers in the current version.
TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
SLLS509E − AUGUST 2001 − REVISED JUNE 2010
38 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Revision History
DATE REV PAGE SECTION DESCRIPTION
3/2/06 B 21 — Near middle of page, changed (FCR0 = 1, IER = 1). to (FCR0 =1, IER1 = 1).
— — Changed from Product Preview to Production Data.
—Typical Characteristics Added Typical Characteristics.
1 Description Split first paragraph into two and started second paragraph on next column to
improve flow.
3, 4 Electrical Characteristics Changed condition note to refer to placeholder Figure XXX.
5, 6
Electrical
Characteristics
(+5V) Changed condition note to refer to placeholder Figure X.
2/25/05
A
7, 8 Electrical Characteristics
(+3.3V) Changed condition note to refer to placeholder Figure XX.
2/25/05
A
910
Changed part number in Figures 6 and 10 to read OPA2832.
9, 10
TilCh titi
Changed condition note to refer to placeholder Figure XXX.
10 Typical Characteristics
(
+5V
)
Added note “One Channel Only” to Figure 11.
12−15
(+5V)
Changed condition note to refer to placeholder Figure X.
13, 14 Changed part number in Figures 29, 32, and 34 to read OPA2832.
17 Typical Characteristics Changed part number in Figure 49 to read OPA2832.
17, 18
Typical
Characteristics
(+3.3V) Changed condition note to refer to placeholder Figure XX.
See
Note Global Product Preview information.
Front Page Diagram Added image title.
1
Logo Changed logo from TI to Burr-Brown Products from Texas Instruments
1Front Page Diagram Added the word “Chebyshev” to diagram title.
2/8/05
*
Features Changed 350V/ns to 350V/μs in sixth bullet.
2/8/05 * 2Pin Out Changed pin out drawing.
3
Electrical Characteristics
Added em-dash (—) to +25°C column of Input Bias Current Drift line under DC
Performance section of table.
3
Electrical
Characteristics
(±5V) Changed columns 2, 3, 4, 5, 7, and 9 to eliminate unnatural breaks in table and
improve appearance.
7, 8 Electrical Characteristics
(+3.3V) Deleted unnecessary sixth column of table.
NOTE:Page numbers for previous revisions may differ from page numbers in the current version.
PACKAGE OPTION ADDENDUM
www.ti.com 28-Jun-2010
Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status (1) Package Type Package
Drawing Pins Package Qty Eco Plan (2) Lead/
Ball Finish MSL Peak Temp (3) Samples
(Requires Login)
TL16C554AFN ACTIVE PLCC FN 68 18 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Request Free Samples
TL16C554AFNG4 ACTIVE PLCC FN 68 18 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Request Free Samples
TL16C554AFNR ACTIVE PLCC FN 68 250 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Purchase Samples
TL16C554AFNRG4 ACTIVE PLCC FN 68 250 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Purchase Samples
TL16C554AIFN ACTIVE PLCC FN 68 18 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Request Free Samples
TL16C554AIFNR ACTIVE PLCC FN 68 250 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Purchase Samples
TL16C554AIPN ACTIVE LQFP PN 80 119 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Request Free Samples
TL16C554AIPNG4 ACTIVE LQFP PN 80 119 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Request Free Samples
TL16C554AIPNR ACTIVE LQFP PN 80 1000 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Purchase Samples
TL16C554AIPNRG4 ACTIVE LQFP PN 80 1000 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Purchase Samples
TL16C554APN ACTIVE LQFP PN 80 119 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Request Free Samples
TL16C554APNG4 ACTIVE LQFP PN 80 119 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Request Free Samples
TL16C554APNR ACTIVE LQFP PN 80 1000 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Purchase Samples
TL16C554APNRG4 ACTIVE LQFP PN 80 1000 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Purchase Samples
TL16CP554AIPM ACTIVE LQFP PM 64 160 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Request Free Samples
TL16CP554APM ACTIVE LQFP PM 64 160 Green (RoHS
& no Sb/Br) CU NIPDAU Level-3-260C-168 HR Request Free Samples
(1) The marketing status values are defined as follows:
PACKAGE OPTION ADDENDUM
www.ti.com 28-Jun-2010
Addendum-Page 2
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
TL16C554AIPNR LQFP PN 80 1000 330.0 24.4 14.6 14.6 1.9 20.0 24.0 Q2
TL16C554APNR LQFP PN 80 1000 330.0 24.4 14.6 14.6 1.9 20.0 24.0 Q2
PACKAGE MATERIALS INFORMATION
www.ti.com 14-Jul-2012
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
TL16C554AIPNR LQFP PN 80 1000 367.0 367.0 45.0
TL16C554APNR LQFP PN 80 1000 367.0 367.0 45.0
PACKAGE MATERIALS INFORMATION
www.ti.com 14-Jul-2012
Pack Materials-Page 2
MECHANICAL DATA
MPLC004A – OCTOBER 1994
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
FN (S-PQCC-J**) PLASTIC J-LEADED CHIP CARRIER
4040005/B 03/95
20 PIN SHOWN
0.026 (0,66)
0.032 (0,81)
D2/E2
0.020 (0,51) MIN
0.180 (4,57) MAX
0.120 (3,05)
0.090 (2,29)
D2/E2
0.013 (0,33)
0.021 (0,53)
Seating Plane
MAX
D2/E2
0.219 (5,56)
0.169 (4,29)
0.319 (8,10)
0.469 (11,91)
0.569 (14,45)
0.369 (9,37)
MAX
0.356 (9,04)
0.456 (11,58)
0.656 (16,66)
0.008 (0,20) NOM
1.158 (29,41)
0.958 (24,33)
0.756 (19,20)
0.191 (4,85)
0.141 (3,58)
MIN
0.441 (11,20)
0.541 (13,74)
0.291 (7,39)
0.341 (8,66)
18
19
14
13
D
D1
13
9
E1E
4
8
MINMAXMIN
PINS
**
20
28
44
0.385 (9,78)
0.485 (12,32)
0.685 (17,40)
52
68
84 1.185 (30,10)
0.985 (25,02)
0.785 (19,94)
D/E
0.395 (10,03)
0.495 (12,57)
1.195 (30,35)
0.995 (25,27)
0.695 (17,65)
0.795 (20,19)
NO. OF D1/E1
0.350 (8,89)
0.450 (11,43)
1.150 (29,21)
0.950 (24,13)
0.650 (16,51)
0.750 (19,05)
0.004 (0,10)
M
0.007 (0,18)
0.050 (1,27)
NOTES: A. All linear dimensions are in inches (millimeters).
B. This drawing is subject to change without notice.
C. Falls within JEDEC MS-018
MECHANICAL DATA
MTQF008A – JANUARY 1995 – REVISED DECEMBER 1996
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PM (S-PQFP-G64) PLASTIC QUAD FLATPACK
4040152/C 11/96
32
17 0,13 NOM
0,25
0,45
0,75
Seating Plane
0,05 MIN
Gage Plane
0,27
33
16
48
1
0,17
49
64
SQ
SQ
10,20
11,80
12,20
9,80
7,50 TYP
1,60 MAX
1,45
1,35
0,08
0,50 M
0,08
0°–7°
NOTES: A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
C. Falls within JEDEC MS-026
D. May also be thermally enhanced plastic with leads connected to the die pads.
MECHANICAL DATA
MTQF010A – JANUARY 1995 – REVISED DECEMBER 1996
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PN (S-PQFP-G80) PLASTIC QUAD FLATPACK
4040135 /B 11/96
0,17
0,27
0,13 NOM
40
21
0,25
0,45
0,75
0,05 MIN
Seating Plane
Gage Plane
41
60
61
80
20
SQ
SQ
1
13,80
14,20
12,20
9,50 TYP
11,80
1,45
1,35
1,60 MAX 0,08
0,50 M
0,08
0°–7°
NOTES: A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
C. Falls within JEDEC MS-026
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