Serial Interface Control Register - NEC mPD780852 Series Preliminary User's Manual

15.3 Serial Interface Control Register

The serial operation mode register 3 (CSIM3) is used to control the serial interface SIO3.
This register is used to set the SIO3's serial clock, operation mode, and operation enable/disable.
CSIM3 is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input clears CSIM3 to 00H.
Caution In the 3-wire serial I/O mode, set the port mode register (PM5X) as follows. Besides that, set
all output latches to 0.
• When serial clock output (Master transmit or master receive)
Set P50 (SCK3) to the output mode (PM50 = 0)
• When serial clock input (Slave transmit or slave receive)
Set P50 to the input mode (PM50 = 1)
• When transmit or transmit/receive mode
Set P51 (SO3) to the output mode (PM51 = 0)
• When receive mode
Set P52 (SI3) to the input mode (PM52 = 1)
Figure 15-2. Serial Operation Mode Register 3 (CSIM3) Format
Address: FF84H After Reset: 00H
Symbol 7
CSIM3 CSIE3
CSIE3
0
1
MODE3
0
1
SCL31
0
0
1
1
Caution Bits 3 to 6 must be set to 0.
Remark f : Main system clock oscillation frequency
X
CHAPTER 15 SERIAL INTERFACE SIO3
R/W
6 5
0 0
SIO3 Operation Enable/Disable Specification
Operation disabled
Operation enabled
Transfer Operation Mode Flag
Transmit or transmit/receive mode
Receive-only mode
SCL30
0 External clock input
2
1 f /2
X
3
0 f /2
X
4
1 f /2
X
Preliminary User's Manual U14581EJ3V0UM00
4 3 2
0 0 MODE3
Shift Register Operation
Operation Mode
Clock Selection
1 0
SCL31 SCL30
203