AT24C01

7

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. Fol-

lowing receipt of the 8-bit data word, the EEPROM will out-

pu t a zer o a nd the add r e ssing device , su ch as a

microcontroller, must terminate the write sequence with a

stop condition. At this time the EEPROM enters an inter-

nally-timed write cycle to the nonvolatile memory. All inputs

are disabled during this write cycle , t

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 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 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 fol-

lowing 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 dis-

abled, acknowledge polling can be initiated. This involves

sending 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 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: 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 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