AT24C01
7
Write Operations
BYTE WR ITE: Following a start condition, a write operation
requires a 7-bit data word address and a low write bit. Upon
receip t of this a ddress, th e EEPROM will again respond
with a zero and then clock in the first 8-bit data word. Fol-
lowing rec eip t of t he 8-b it da ta wo rd , the EE PR OM wil l o ut-
put a zero and the addressing device, such as a
microcontr oller, mus t terminate th e write s equence with a
stop condition. At this time the EEPROM enters an inter-
nally-timed write cycle to the nonvolatile memory. All inputs
are disa ble d durin g thi s write cycl e , tWR, and the EE P RO M
will not respond until the write is c omplete (refer to Figure
1).
PAGE WRITE: The AT24 C01 is capable of a 4-byte pag e
write.
A page write is initiated the same as a byte write but the
microcontroller does not send a stop condition after the first
data word is clocked in. Instead, after the EEPROM
acknowledges receipt of the first data word, the microcon-
troller can transmit up to three more data words. The
EEPROM will respond with a zero after each data word
received. The microcontroller must terminate the page
write sequence with a stop condition (refer to Figure 2).
The data word address lower 2 bits are internally incre-
mented fol low ing the re ce ipt of e ac h da ta wo rd . The h ig her
five data word address bits are not incremented, retaining
the memory page row location. W hen the word address,
inter nally gene rated, rea ches the p age bounda ry, the fol-
lowing byte is p lac ed at the begi nnin g of the s ame page . If
more than four data words are transmitted to the EEPROM,
the data word add ress wil l “roll over ” and previou s data will
be overwritten.
ACKNOWLEDGE POLLING: Once the internally-timed
write cycle ha s started and the EEPROM inputs are dis-
abled, acknowl edge polling can be initia ted. This invol ves
sending a start condition followed by the devic e address
word. The rea d/write bit is repr esentative of the operation
desired. O nly if the internal write cycl e has completed will
the EEPROM respond with a zero allowing the read or
write sequence to continue.
Read Operations
Read operations are initiated the same way as write opera-
tions with the exception that the read/write select bit in the
device address word is set to one. There are two read
operations: byte read and sequential read.
BYTE READ: A byte read is initiated with a start condition
followed by a 7-bit data word address and a high read bit.
The AT24C01 will respond with an acknowledge and then
serially output 8 data bits. The microcontroller does not
respond with a zero but does generate a following stop
condition (refer to Figure 3).
SEQUENTIAL READ: Seq uential read s are initiate d the
same as a byt e rea d. Aft er th e micr ocon troll er rec eives an
8-bit data word, it responds with an acknowledge. As long
as the EEPROM re ceives an acknowledge, it will continue
to incr ement the da ta word addr ess and ser ially cl ock out
sequential d ata words. Whe n the memo ry address limi t is
reached, the data word address will “roll over” and the
sequential read will co ntinue. The sequential read opera-
tion is terminated when the microcontroller does not
respond with an input zero but does generate a following
stop condition (refer to Figure 4).
Figure 1. Byte Write