8 Read Operations
Read operations are initiated in a similar way as write operations with
the exception that the Read/Write select bit in the device address
byte must be set to a logic ‘1’. There are multiple read operations
supported by the device:
- Current Address Read within the EEPROM
- Random Read within the EEPROM
- Sequential Read within the EEPROM
- Read from the Security Register
- Manufacturer ID Read
Note: The AT21CS01/AT21CS11 contains a single, shared-memory Address Pointer that maintains the
address of the next byte in the EEPROM or Security register to be accessed. For example,
if the last byte read is memory location 0Dh of the EEPROM, then the Address Pointer
will be pointing to memory location 0Eh of the EEPROM. As such, when changing from a
read in one region to the other, the first read operation in the new region should begin
with a random read instead of a current address read to ensure the Address Pointer is
set to a known value within the desired region.
If the end of the EEPROM or the Security register is reached, then the Address Pointer will “roll over” to the beginning address of that region. The Address Pointer retains its value between operations as long as the pull-up voltage on the SI/O pin is maintained or as long as the device has not been reset.