8
AT24C01
0134G–SEEPR–7/03
Write Operations BYTE WRITE: Following a start condition, a write operation requires a 7-bit data word
address and a low write bit. Upon receipt of this address, the EEPROM will again
respond with a zero and then clock in the first 8-bit data word. Following receipt of the 8-
bit data word, the EEPROM will output a zero and the addressing device, such as a
microcontroller, must terminate the write sequence with a stop condition. At this time the
EEPROM enters an internally-timed write cycle to the nonvolatile memory. All inputs are
disabled during this write cycle , t
WR
, and the EEPROM will not respond until the write is
complete (refer to Figure 1).
PAGE WRITE: The AT24C01 is capable of a 4-byte page 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 microcontroller 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 incremented following the receipt of
each data word. The higher five data word address bits are not incremented, retaining
the memory page row location. When the word address, internally generated, reaches
the page boundary, the following byte is placed at the beginning of the same page. If
more than four data words are transmitted to the EEPROM, the data word address will
“roll over” and previous data will be overwritten.
ACKNOWLEDGE POLLING: Once the internally-timed write cycle has started and the
EEPROM inputs are disabled, acknowledge polling can be initiated. This involves send-
ing a start condition followed by the device address word. The read/write bit is
representative of the operation desired. Only if the internal write cycle 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 operations 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: Sequential reads are initiated the same as a byte read. After the
microcontroller receives an 8-bit data word, it responds with an acknowledge. As long as
the EEPROM receives an acknowledge, it will continue to increment the data word
address and serially clock out sequential data words. When the memory address limit is
reached, the data word address will “roll over” and the sequential read will continue. The
sequential read operation is terminated when the microcontroller does not respond with
an input zero but does generate a following stop condition (refer to Figure 4).
