
CHAPTER 15 SERIAL INTERFACE CHANNEL 1
246
CSIE1
CSIMPM20 P20 PM21 P21 PM22 P22
Shift Register
1 Operation
Serial Clock Counter
Operation Control
SI1/P20
Pin Function
SO1/P21
Pin Function
SCK1/P22
Pin Function
Note 1
Note 1
Note 1
Note 1
Note 1
Note 1
P20
(CMOS
input/output)
P21
(CMOS
input/output)
P22
(CMOS
input/output)
0
×
Operation stop
Clear
SCK1
(Input)
0
Note 2
1
Note 2
1
×
SI1
Note 2
(Input)
SO1
1
0
0
Operation enable Count operation
1
0
1
(CMOS output)
SCK1
(CMOS output)
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
×
: don’t care
PMxx: Port mode register
Pxx: Port output latch
15.4 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
15.4.1 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 clears 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