8.3 Sequential Read within the EEPROM

Sequential reads start as either a current address read or as a random read. However, instead of the host sending a NACK (logic ‘1’) response to end a read operation after a single byte of data has been read, the host sends an ACK (logic ‘0’) to instruct the AT21CS01/AT21CS11 to output another byte of data. As long as the device receives an ACK from the host after each byte of data has been output, it will continue to increment the address counter and output the next byte of data from the EEPROM. If the end of the EEPROM is reached, then the Address Pointer will “roll over” to the beginning (address 00h) of the EEPROM region. To end the sequential read operation, the host must send a NACK response after the device has output a complete byte of data. After the device receives the NACK, it will end the read operation and return to Standby mode.

Note: If the last operation to the device accessed the Security register, then a random read should be performed to ensure that the Address Pointer is set to a known memory location within the EEPROM.

Figure 8-3. Sequential Read from a Current Address Read

Figure 8-4. Sequential Read from a Random Read