I2C Port
CS4953xx Hardware Users Manual
DS732UM7
Copyright 2008 Cirrus Logic, Inc
3-4
3.2.2 I
2
C Bus Dynamics
The Start condition for an I
2
C transaction is defined as the first falling edge on the SCP1_SDA line while
SCP1_CLK is high. An I
2
C Stop condition is defined as the first rising edge on the SCP1_SDA line while
SCP1_CLK is high. Hence for valid data transfer, SCP1_SDA must remain stable during the high period of the clock
pulse. Start and Stop conditions are always generated by the master. The bus is considered to be busy after the Start
condition. The bus is considered to be free again following the Stop condition. The bus stays busy if a repeated Start
condition is generated instead of a Stop condition. In this respect, the Start and repeated Start conditions are
functionally identical.
Figure 3-3. I
2
C Start and Stop Conditions
SCP2_CLK
I
2
C Control Port Bit Clock.
In master mode, this pin serves as the serial control clock
output (open drain in I
2
C mode / output in SPI mode). In serial
slave mode, this pin serves as the serial control clock input. In
I
2
C slave mode the clock can be pulled low by the port to stall
the master.
103
1
Open
Drain
SCP2_SDA
Bidirectional Data I
2
C Mode Master/Slave Data IO. In I
2
C
master and slave mode, this open drain pin serves as the data
input and output.
105
2
Open
Drain
SCP2_IRQ
Serial Control Port Data Ready Interrupt Request, Output,
Active Low.
This pin is driven low when the DSP has a message for the host
to read. The pin will go high when the host has read the
message and the DSP has no further messages.
108
5
Open
Drain
Table 3-1. Serial Control Port 1 I
2
C Signals (Continued)
Pin Name
Pin Description
LQFP-144
Pin #
LQFP-128
Pin #
Pin
Type
SCP1_CLK
SCP1_SDA
Start
SCP1_CLK
SCP1_SDA
Stop
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