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CHAPTER 14 SERIAL INTERFACE CHANNEL 1
268
User
’
s Manual U11302EJ4V0UM
CSIM
11
Shift register
1 operation
Serial clock counter
operation control
SI1/P20
pin function
SO1/P21
pin function
SCK1/P22
pin function
CSIE1
PM20 P20
PM21
P21
PM22
P22
Note 1 Note 1 Note 1 Note 1 Note 1 Note 1
Operation stop
Clear
P20
P21
P22
0
×
(CMOS I/O)
(CMOS I/O)
(CMOS I/O)
Operation enable Count operation
SI1
Note 2
(input)
SO1
SCK1
(input)
0
1
×
Note 2 Note 2
1
(CMOS output)
1
×
0
0
SCK1
1
0
1
(CMOS output)
Notes 1.
Can be used freely as a port pin.
2.
Can be used as P20 (CMOS I/O) when used only for transmission (set bit 7 (RE) of the automatic
data transmit/receive control register (ADTC) to 0).
Remark
×
:
PM
××
: Port mode register
P
××
:
Port output latch
don
’
t care
14.4 Operations of Serial Interface Channel 1
The following three operating modes are available for serial interface channel 1.
Operation stop mode
3-wire serial I/O mode
3-wire serial I/O mode with automatic transmit/receive function
14.4.1 Operation stop mode
Serial transfer is not carried out in the operation stop mode. Thus, power consumption can be reduced. Serial
I/O shift register 1 (SIO1) does not carry out shift operations and 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 I/O ports.
(1) Register setting
The operation stop mode is set by 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.
CSIE1
DIR
ATE
0
0
0
CSIM
11
CSIM
10
<7>
6
<5>
4
3
2
1
0
CSIM1
Symbol
FF68H 00H R/W
Address After reset R/W