Write Operations

BYTE WRITE: A write operation requires an 8-bit data word address follo wing the device address

wo rd and acknowledgm en t. Upon receipt of this address, the EEPROM will again respond with a "0" and

then clock in the first 8-bit data word. Following receipt of the 8-bit data word, the EEPROM will output a

"0" 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, tWR, to the nonvolatile memory.

All inputs are disabled during this write cycle and the EEPROM will not respond until the write is comp lete

(see Figure 5 ).

PAGE WRITE: The 2K EEPROM is capable of an 8-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 seven (2K) more data words. The EEPROM will respond with a "0" after

each data word received. The microcontroller must terminate the page write sequence with a stop condition

(see Figure 6 ).

The data word address lower three (2K) bits are internally incremented following the receipt of each data

word. The higher 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 eight (2K) 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, acknowled ge 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 "0", allowi ng 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 "1". There are three read operations: current address read, random

address read and sequential read.

CURRENT ADDRESS READ: The internal data word address counter maintains the last accessed

address, and incremented by one.*This address stays valid between operations as long as the chip

power is maintained. The address "roll over" during read is from the last byte of the last memory page

to the first byte of the first page.The address "roll over" during write is from the last byte of the current

page to the first byte of the same page.

Once the device address with the read/write select bit set to "1" is clocked in and acknowledged by the

EEPROM, the current address data word is serially clocked out. The microcontroller does not respond

with an input "0" but does generate a following stop condition (see Figure 7 ).

V2.1

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