3-7
Copyright 2008 Cirrus Logic, Inc.
DS732UM7
I2C Port
CS4953xx Hardware Users Manual
Figure 3-7. Stop Condition with ACK and NACK
If a slave can’t receive or transmit another complete byte of data until it has performed some other function, for
example servicing an internal interrupt, it can hold the SCP1_CLK line low to force the master into a wait state. Data
transfer then continues when the slave is ready for another byte of data and releases SCP1_CLK.
3.2.3 I
2
C Messaging
Messaging to the CS4953xx using the I
2
C bus requires usage of all the information provided in the above I
2
C
Section 3.2.1 “I2C System Bus Description” on page 3-2
and
Section 3.2.2 “I2C Bus Dynamics” on page 3-4
.
Every I
2
C transaction to the CS4953xx will involve 4-byte words used for control and application image download.
A detailed description of the serial SPI communication mode is provided in this section. This includes:
•
A flow diagram and description for a serial I
2
C write
•
A flow diagram and description for a serial I
2
C read
3.2.3.1 SCP1_BSY Behavior
The SCP1_BSY signal is not part of the I
2
C protocol, but it is provided so that the slave can signal to the master that
it cannot receive any more data. It performs the same function as that of holding SCP1_CLK low to halt
transmission. A falling edge of the SCP1_BSY signal indicates the master must halt transmission. Once the
SCP1_BSY signal goes high, the suspended transaction may continue. It is important for the host to obey the
SCP1_BSY pin status for proper communication with the DSP.
Stop
SCP1_CLK
SCP1_SDA
Data Byte
ACK
M
S
M
Write
Read
S
M
M
Stop
SCP1_CLK
SCP1_SDA
Data Byte
NACK
M
S
M
Write
Read
S
M
M
M = Master Drives SDA
S = Slave Drives SDA
Содержание CS4953xx
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