2
PIN NAMES
DEVICE OPERATION
The UT8Q512 has three control inputs called Enable 1 (E), Write
Enable (W), and Output Enable (G); 19 address inputs, A(18:0);
and eight bidirectional data lines, DQ(7:0). E Device Enable
controls device selection, active, and standby modes. Asserting
E enables the device, causes IDD to rise to its active value, and
decodes the 19 address inputs to select one of 524,288 words in
the memory. W controls read and write operations. During a read
cycle, G must be asserted to enable the outputs.
Table 1. Device Operation Truth Table
Notes:
1. “X” is defined as a “don’t care” condition.
2. Device active; outputs disabled.
READ CYCLE
A combination of W greater than VIH (min) and E less than VIL
(max) defines a read cycle. Read access time is measured from
the latter of Device Enable, Output Enable, or valid address to
valid data output.
SRAM Read Cycle 1, the Address Access in figure 3a, is
initiated by a change in address inputs while the chip is enabled
with G asserted and W deasserted. Valid data appears on data
outputs DQ(7:0) after the specified tAV Q V is satisfied. Outputs
remain active throughout the entire cycle. As long as Device
Enable and Output Enable are active, the address inputs may
change at a rate equal to the minimum read cycle time (tAVAV ).
SRAM read Cycle 2, the Chip Enable - Controlled Access in
figure 3b, is initiated by E going active while G remains asserted,
W remains deasserted, and the addresses remain stable for the
entire cycle. After the specified tETQV is satisfied, the eight-bit
word addressed by A(18:0) is accessed and appears at the data
outputs DQ(7:0).
SRAM read Cycle 3, the Output Enable - Controlled Access in
figure 3c, is initiated by G going active while E is asserted, W
is deasserted, and the addresses are stable. Read access time is
tGLQV unless tAVQV or tETQV have not been satisfied.
A(18:0) Address
DQ(7:0) Data Input/Output
EEnable
WWrite Enable
GOutput Enable
VDD Power
VSS Ground
136
235
334
433
532
631
730
829
928
10 27
11 26
12 25
13 24
14 23
15 22
16 21
17 20
18 19
Figure 2. 25ns SRAM Pinout (36)
NC
A18
A17
A16
A15
G
DQ7
DQ6
VSS
VDD
DQ5
DQ4
A14
A13
A12
A11
A10
NC
A0
A1
A2
A3
A4
E
DQ0
DQ1
VDD
VSS
DQ2
DQ3
W
A5
A6
A7
A8
A9
G W E I/O Mode Mode
X1X 1 3-state Standby
X 0 0 Data in Write
1103-state Read2
010Data out Read