ACE24C16A

Two-wire Serial EEPROM

VER 1.2

9

MSB

LSB

1

0

1

0

R/W

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 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 one 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 zero but does generate a following stop condition (refer to Figure 10).

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 zero but does generate a following stop condition (refer to Figure 11).

Sequential Read

Sequential reads are initiated by either a current address read or a random address read. After the

microcontroller receives a 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 a zero but does generate a following stop condition (refer to

Figure 12).

16K

Figure 7．Device Address