NEC PD78F9488 - Manual (Page 190)

CHAPTER 11 SERIAL INTERFACE 20
190
User’s Manual U15331EJ4V1UD
11.3 Serial Interface 20 Control Registers
Serial interface 20 is controlled by the following six registers.
• Serial operation mode register 20 (CSIM20)
• Asynchronous serial interface mode register 20 (ASIM20)
• Asynchronous serial interface status register 20 (ASIS20)
• Baud rate generator control register 20 (BRGC20)
• Port mode register 2 (PM2)
• Port 2
(1) Serial operation mode register 20 (CSIM20)
CSIM20 is used to make the settings related to 3-wire serial I/O mode.
CSIM20 is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets CSIM20 to 00H.
Figure 11-3. Format of Serial Operation Mode Register 20
CSIE20
0
1
3-wire serial I/O mode operation control
CSIE20 0 0 0 0 DIR20 CSCK20 0 CSIM20
Symbol Address After reset R/W
FF72H 00H R/W
<7> 6 5 4 3 2 1 0
Operation disabled
Operation enabled
DIR20
0
1
First-bit specification
MSB
LSB
CSCK20
0
1
3-wire serial I/O mode clock selection
External clock input to the SCK20 pin
Output of the dedicated baud rate generator
Cautions 1. Bits 0 and 3 to 6 must be set to 0.
2. CSIM20 must be cleared to 00H if UART mode is selected.
3. When the external input clock is selected in 3-wire serial I/O mode, set input mode by
setting bit 0 of port mode register 2 (PM2) to 1.
4. Switch operating modes after halting the serial transmit/receive operation.