ACE24C64BD Datasheet, PDF (7/17 Pages) ACE Technology Co., LTD. – Two-wire Serial EEPROM

ACE24C64BD
Two-wire Serial EEPROM
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).
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 “0” but does generate a following stop condition (see Figure 9).
Figure 4: Device Address
Figure 5: Byte write
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