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19.4 Serial Interface Channel 1 Operations
The following three operating modes are available to the serial interface channel 1.
•
Operation stop mode
•
3-wire serial I/O mode
•
3-wire serial I/O mode with automatic transmit/receive function
19.4.1 Operation stop mode
Serial transfer is not carried out in the operation stop mode. Thus, power consumption can be reduced. The
serial I/O shift register 1 (SIO1) does not carry out shift operation either, and thus it can be used as an ordinary
8-bit register.
In the operation stop mode, the P20/SI1, P21/SO1, P22/SCK1, P23/STB, and P24/BUSY pins can be used as
ordinary input/output ports.
(1) Register setting
The operation stop mode is set with the serial operating mode register 1 (CSIM1).
CSIM1 is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets CSIM1 to 00H.
Symbol
<7>
6
<5>
CSIM1 CSIE1 DIR
ATE
CSIE
CSIM
PM20
P20 PM21 P21 PM22
1
11
Note 1
Note 1 Note 1 Note 1 Note 1
0
x
x
x
0
Note 2
Note 2
1
1
x
1
Notes 1. Can be used freely as port function.
2. Can be used as P20 (CMOS input/output) when only transmitter is used (set bit 7 (RE) of the
automatic data transmit/receive control register (ADTC) to 0).
Remark x
: Don't care
PMxx : Port mode register
Pxx
: Port output latch
CHAPTER 19 SERIAL INTERFACE CHANNEL 1
4
3
2
1
0
0
0
CSIM11 CSIM10
Shift Register
P22
1 Operation
Note 1
Operation
x
x
x
x
stop
1
x
Operation
0
0
enable
0
1
0
Address
After Reset
FF68H
00H
Serial Clock Counter
SI1/P20 Pin
Operation Control
Function
Clear
P20 (CMOS
input/output)
Count
SI1
Note 2
(Input)
operation
R/W
R/W
SO1/P21 Pin
SCK1/P22
Function
Pin Function
P21 (CMOS
P22 (CMOS
input/output)
input/output)
SCK1
(Input)
SO1 (CMOS
output)
SCK1
(CMOS
output)
425
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