Figure 3-6. stop condition with ack and nack – Cirrus Logic CS485xx User Manual
Page 38
Serial Control Port Configuration
CS485xx Hardware User’s Manual
DS734UM7
Copyright 2009 Cirrus Logic, Inc.
3-6
Figure 3-5. Data Byte with ACK and NACK
After an ACK or NACK from the master or slave, the slave must leave the SCP_SDA line high so the master
can then generate either a Stop condition to abort the transfer, or a another Start condition to start a new
transfer.
Figure 3-6. 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 SCP_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 SCP_CLK.
Start
SCP_CLK
SCP_SDA
A[6]
A[5]
A[4]
A[3]
A[2]
A[1]
A[0]
R/W
ACK
Data Byte
ACK
M
S
M
S
Write
M
S
S
M
Read
Start
SCP_CLK
SCP_SDA
A[6]
A[5]
A[4]
A[3]
A[2]
A[1]
A[0]
R/W
ACK
Data Byte
NACK
M
S
M
S
Write
M
S
S
M
Read
M = Master Drives SDA
S = Slave Drives SDA
Stop
SCP_CLK
SCP_SDA
Data Byte
ACK
M
S
M
Write
Read
S
M
M
Stop
SCP_CLK
SCP_SDA
Data Byte
NACK
M
S
M
Write
Read
S
M
M
M = Master Drives SDA
S = Slave Drives SDA