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CHAPTER 5 PERIPHERAL HARDWARE FUNCTIONS
Table 5-10. Various Signals Used in the SBI Mode (1/2)
SCK
SB0, SB1
“H”
“H”
SCK
SB0, SB1
Rising edge of SB0 or 
SB1 when SCK = 1
Falling edge of SB0 or
SB1 when SCK = 1
Low level signal
output on SB0 or SB1 
during one SCK clock
cycle after serial 
reception is completed
[Synchronous BUSY signal]
Low level signal output on 
SB0 or SB1 after 
acknowledge signal
High level signal 
output on SB0 or SB1
before serial transfer 
is started or after 
serial transfer is 
completed
Bus release signal
(REL)
Command signal
(CMD)
Acknowledge
signal
(ACK)
Busy signal
(BUSY)
Ready signal
(READY)
Output
device Definition
• RELT is set.
• CMDT is set.
<1> ACKE = 1
<2> ACKT is set.
• BSYE = 1
<1> BSYE = 0
<2>
Execution of 
instruction to
write data to 
SIO (Transfer 
start request)
Condition for
output
• RELD is set.
• CMDD is clear-
ed.
• CMDD is set.
• ACKD is set.
Flag
operation Meaning
of signal
Indicates that CMD 
signal follows and 
data transmitted is 
address data.
i) Data transmitted 
after REL signal 
output is address.
ii) Data transmitted, 
with REL signal 
not being output, 
is command.
Indicates completion 
of reception.
Indicates that serial 
reception is disabled 
because processing 
is in progress.
Indicates that serial
reception is enabled. 
Signal name Timing chart
READY
READY
ACK
SCK
D0
D0
SB0, SB1
9
BUSY
ACK
BUSY

Master
Master
Master/
slave
Slave
Slave
[Synchronous BUSY output]
SB0, SB1