ACE24LA1024A

Two-wire Serial EEPROM

VER 1.3

8

The data word address lower eight 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 256 data words are transmitted to the EEPROM, the data

word address will "roll over" and previous data will be overwritten.

Write Identification Page:

The Identification Page (256 bytes) is an additional page which can be written and (later) permanently

locked in Read-only mode. It is written by issuing the Write Identification Page instruction. This instruction

uses the same protocol and format as Page Write (into memory array), except for the following

differences:



Device type identifier = 1011b



MSB address bits B16/B8 are don't care except for address bit B10 which must be "0".

LSB address bits B7/B0 define the byte address inside the Identification page.

If the Identification page is locked, the data bytes transferred during the Write Identification Page

instruction are not acknowledged (NoAck).

Acknowledge Polling:

Once the internally timed write cycle has started and the EEPROM inputs are disabled, 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 "0", 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 "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 address accessed during the last read or write

operation, 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).