ACE24LA64A

Two-wire Serial EEPROM

VER 1.1

7

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

disabled during this write cycle and the EEPROM will not respond until the write is complete (see Figure

6).

The data word address lower five 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 32 data words are transmitted to the EEPROM, the data word

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

Acknowledge Polling:

The Identification Page (32 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:

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).

Random Read:

A random read requires a “dummy” byte write sequence to load in the data word address. Once the

device address word and data word address are clocked in and acknowledged by the EEPROM, the

microcontroller must generate another start condition. The microcontroller now initiates a current address

read by sending a device address with the read/write select bit high. The EEPROM acknowledges the

device address and serially clocks out the data word. The microcontroller does not respond with a

“0” but

does generate a following stop condition (see Figure 8).