The gas gauge supports the standard I²C read, incremental read, one-byte write quick read, and functions. The 7-bit device address (ADDR) is the most significant 7 bits of the hex address and is fixed as 1010101. The 8-bit device address is therefore 0xAA or 0xAB for write or read, respectively.

Figure 7-1 Supported I²C formats: (a) 1-byte write, (b) quick read, (c) 1 byte-read, and (d) incremental read (S = Start, Sr = Repeated Start, A = Acknowledge, N = No Acknowledge, and P = Stop).

The “quick read” returns data at the address indicated by the address pointer. The address pointer, a register internal to the I²C communication engine, increments whenever data is acknowledged by the device or the I²C master. “Quick writes” function in the same manner and are a convenient means of sending multiple bytes to consecutive command locations (such as 2-byte commands that require two bytes of data).

Figure 7-2 Attempt To Write a Read-Only Address (Nack After Data Sent By Master)

Figure 7-3 Attempt To Read An Address Above 0x7F (Nack Command)

Figure 7-4 Attempt At Incremental Writes (nack All Extra Data Bytes Sent)

Figure 7-5 Incremental Read at the Maximum Allowed Read Address

The I²C engine releases both SDA and SCL if the I²C bus is held low for t_BUSERR. If the gas gauge was holding the lines, releasing them frees the master to drive the lines. If an external condition is holding either of the lines low, the I²C engine enters the low-power SLEEP mode.