IS31AP2121
Integrated Silicon Solution, Inc. – www.issi.com
22
Rev. C, 10/20/2015
I2C-BUS TRANSFER PROTOCOL
INTRODUCTION
IS31AP2121 employs I2C-bus transfer protocol. Two
wires, serial data and serial clock carry information
between the devices connected to the bus. Each
device is recognized by a unique 7-bit address and
can operate as either a transmitter or a receiver. The
master device initiates a data transfer and provides
the serial clock on the bus. IS31AP2121 is always
an I2C slave device.
PROTOCOL
START and STOP Condition
START is identified by a high to low transition of the
SDA signal. A START condition must precede any
command for data transfer. A STOP is identified by a
low to high transition of the SDA signal. A STOP
condition terminates communication between
IS31AP2121 and the master device on the bus. In
both START and STOP, the SCL is stable in the
high state.
Data Validity
The SDA signal must be stable during the high
period of the clock. The high or low change of SDA
only occurs when SCL signal is low. IS31AP2121
samples the SDA signal at the rising edge of SCL
signal.
Device Addressing
The master generates 7-bit address to recognize
slave devices. When IS31AP2121 receives 7-bit
address matched with 0110000 or 0110001
(ERRORB pin state during power up), IS31AP2121
will acknowledge at the 9th bit (the 8th bit is for R/W
bit). The bytes following the device identification
address are for IS31AP2121 internal sub-addresses.
Data Transferring
Each byte of SDA signaling must consist of 8
consecutive bits, and the byte is followed by an
acknowledge bit. Data is transferred with MSB first,
as shown in the figure below. In both write and read
operations, IS31AP2121 supports both single-byte
and multi-byte transfers. Refer to the figure below for
detailed data-transferring protocol.
Figure 35
Data Transferring
REGISTER DEFINITIONS
The IS31AP2121’s audio signal processing data flow is shown below. Users can control these functions by
programming appropriate settings in the register table. In this section, the register table is summarized first. The
definition of each register follows in the next section.