AT24C256C_09 Datasheet, PDF (11/21 Pages) ATMEL Corporation – Two-wire Serial EEPROM

AT24C256C [Preliminary]
6. 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.
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 (refer to Figure 11).
Figure 11. Current Address Read
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. (Refer to
Figure 12)
Figure 12. Random Read
Note: * = DON’T CARE bit
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8568A–SEEPR–9/09