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CHAPTER 13
SERIAL INTERFACE SIO0
User’s Manual U12790EJ2V0UD
(2) Slave wait release
The slave wait release operation is performed by setting the WREL flag or executing an SIO0 write instruction.
If the slave sends data, the wait is immediately released by execution of an SIO0 write instruction and the
clock rises without the start transmission bit being output on the data line. Therefore, as shown in Figure 13-
47, data should be transmitted by manipulating the P27 output latch via the program. At this time, control
the low-level width ("a" in Figure 13-47) of the first serial clock at the timing used for setting the P27 output
latch to 1 after execution of an SIO0 write instruction.
In addition, if the acknowledge signal from the master is not output (if data transmission from the slave is
completed), set the WREL flag of SINT0 to 1 and release the wait.
If the slave receives data, after execution of an SIO0 write instruction, it is not necessary to manipulate the
P27 output latch because the data to be received has already been output on the data line even if the wait
is released.
For the timing of these operations, see Figures 13-44 and 13-45.
Figure 13-47. Slave Wait Release (Transmission)
(3) Reception completion of slave
During processing of reception completion by a slave device, confirm the statuses of CMDD and COI (if CMDD
= 1). This procedure is necessary to use the wakeup function normally. If an uncertain amount of data is
sent from the master device, the slave device cannot determine whether the start condition signal or the data
will be sent from the master. This may disable use of the wakeup function.
Writing
FFH
to SIO0
Setting
CSIIF0
Setting
ACKD
Serial reception
9
a
23
A0
R/W
ACK
D7
D6
D5
P27
output
latch 1
Setting
CSIIF0
ACK
output
Serial transmission
Write
data
to SIO0
P27
output
latch 0
Wait
release
Software operation
Hardware operation
SCL
Software operation
Hardware operation
Transfer line
Master device operation
Slave device operation
1
SDA0 (SDA1)