6.1 Device Addressing

Accessing the device requires an 8‑bit device address byte following a Start condition to enable the device for a read or write operation.

The Most Significant four bits of the device address byte is referred to as the device type identifier. The device type identifier ‘1010’ (Ah) is required in bits 7 through 4 of the device address byte (see Table 6-1).

The AT24CS16 utilizes a separate memory block containing a factory programmed 128-bit serial number. Access to this memory location is similar to the EEPROM region with the exception that the device type identifier is set to ‘1011’ (Bh) in bits 7 through 4 of the device address byte (see Table 6-1).

Following the 4-bit device type identifier in the bit 3, bit 2 and bit 1 position of the device address byte are bits A10, A9 and A8 which are the three Most Significant bits of the memory array word address.

The eighth bit (bit 0) of the device address byte is the Read/Write Select bit. A read operation is initiated if this bit is high and a write operation is initiated if this bit is low.

Upon the successful comparison of the device address byte, the AT24CS16 will return an ACK. If a valid comparison is not made, the device will NACK.

For all operations except the current address read, a word address byte must be transmitted to the device immediately following the device address byte. The word address byte consists of the remaining eight bits of the 11‑bit memory array word address and is used to specify which byte location in the EEPROM to start reading or writing. Refer to Table 6-2 to review these bit positions.