CHAPTER 15 SERIAL INTERFACE CHANNEL 1
247
CSIM CSIM
11
Serial Interface Channel 1 Clock Selection
10
0
×
Clock externally input to SCK1 pin
Note 1
1
0
8-bit timer register 2 (TM2) output
1
1
Clock specified with bits 4 to 7 of timer clock select register 3 (TCL3)
ATE
Serial Interface Channel 1 Operating Mode Selection
0
3-wire serial I/O mode
1
3-wire serial I/O mode with automatic transmit/receive function
DIR
Start Bit
SI1 Pin Function
SO1 Pin function
0
MSB
SI1/P20 (Input)
SO1 (CMOS output)
1
LSB
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 2
Note 2
Note 2
Note 2
Note 2
Note 2
P20
(CMOS
input/output)
P21
(CMOS
input/output)
P22
(CMOS
input/output)
0
×
Operation stop
Clear
SCK1
(Input)
0
Note 3
1
Note 3
×
1
×
SI1
Note 3
(Input)
SO1
1
0
0
Operation enable Count operation
1
0
1
(CMOS output)
SCK1
(CMOS output)
Notes 1.
If the external clock input has been selected with CSIM11 set to 0, set bits 1 (BUSY1) and 2 (STRB)
of the automatic data transmit/receive control register (ADTC) to 0, 0.
2.
Can be used freely as port function.
3.
Can be used as P20 when only transmitter is used. (Set bit 7 (RE) of ADTC to 0.)
Remark
×
: don’t care
PMxx: Port mode register
Pxx: Port output latch
15.4.2 3-wire serial I/O mode operation
The 3-wire serial I/O mode is valid for connection of peripheral I/O units and display controllers which
incorporate a conventional synchronous serial interface as is the case with the 75X/XL, 78K and 17K Series.
Communication is carried out with three lines of serial clock (SCK1), serial output (SO1) and serial input (SI1).
(1) Register setting
The 3-wire serial I/O 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