5 Device Addressing and I²C Protocol Emulation

Accessing the device requires a Start condition followed by an 8-bit device address byte.

The single-wire protocol sequence emulates what would be required for an I²C Serial EEPROM, with the exception that the beginning four bits of the device address are used as an opcode for the different commands and actions that the device can perform.

Since multiple client devices can reside on the bus, each client device must have its own unique address so that the host can access each device independently. After the 4-bit opcode, the following three bits of the device address byte are comprised of the client address bits. The three client address bits are preprogrammed prior to shipment. Obtaining devices with different client address bit values is done by purchasing a specific ordering code. Refer to Packaging Information for an explanation of which ordering code corresponds with a specific client address value.

Following the three client address bits is a Read/Write select bit where a logic ‘1’ indicates a read and a logic ‘0’ indicates a write. Upon the successful comparison of the device address byte, the EEPROM will return an ACK (logic ‘0’). If the 4-bit opcode is invalid or the three bits of the client address do not match what is preprogrammed in the device, the device will not respond on the SI/O line and will return to a Standby state.

Following the device address byte, a memory address byte must be transmitted to the device immediately. The memory address byte contains a 7-bit memory array address to specify which location in the EEPROM to start reading or writing. Refer to Table 5-2 to review these bit positions.