Feb 1, 2023 Page 10 of 34 Rev 1.1
5.1.1 2-Wire-Serial Control and Data Bus (I2C Style Interface)
The serial interface provides a 2-wire bidirectional read/write data interface similar to and typically compatible with
standard I2C protocol. This protocol defines any device that sends CLK onto the bus as a master, and the receiving
device as slave. The NAU8224 can function only as a slave device.
An external clockdrivesthe device, and in accordance with the protocol,data is sent to or from thedevice accordingly.
All functions are controlled by means of a register control interface in the device.
5.1.2 2-Wire Protocol Convention
All 2-Wire interface operations must begin with a START condition, which is a HIGH-to-LOW transition of SDIO
while SCLK is HIGH. All 2-Wire interface operations are terminated by a STOP condition, which is a LOW to HIGH
transition of SDIO while SCLK is HIGH. A STOP condition at the end of a read or write operation places the serial
interface in standby mode.
An acknowledge (ACK), is a software convention is used to indicate a successful data transfer. The transmitting
device releases the SDIO bus after transmitting eight bits to allow for the ACK response. During the ninth clock
cycle, the receiver pulls the SDIO line LOW to acknowledge the reception of the eight bits of data.
Following a START condition, the master must output a device address byte. This consists of a 7-bit device address,
and the LSB of the device address byte is the R/W (Read/Write) control bit. When R/W= 1, this indicates the master
is initiating a read operation from the slave device, and when R/W=0, the master is initiating a write operation to the
slave device. If the device address matches the address of the slave device, the slave will output an ACK during the
period when the master allows for the ACK signal.
START and STOP signals
9
8
12 ...7
Acknowledge
SCLK
SDIO
Not Acknowledge
Acknowledge and NOT Acknowledge
