UPD780078 Datasheet, PDF (313/592 Pages) NEC – 8-Bit Single-Chip Microcontrollers

CHAPTER 16 SERIAL INTERFACE SIO3
(2) Port mode register 3 (PM3)
PM3 is a register that sets the input/output of port 3 in 1-bit units.
To use the P35/SO3/RxD2 pin as a serial data output, set PM35 and the output latch of P35 to 0.
To use the P34/SI3/TxD2 pin as a serial data input, and the P36/ASCK2/SCK3 pin as a clock input, set PM34
to 1.
At this time, the output latches of P34 and P36 can be either 0 or 1.
PM3 is set by a 1-bit or 8-bit memory manipulation instruction.
RESET input sets PM3 to FFH.
Figure 16-3. Format of Port Mode Register 3 (PM3)
Address: FF23H After reset: FFH
Symbol
7
6
PM3
1
PM36
R/W
5
PM35
4
PM34
3
PM33
2
PM32
1
PM31
0
PM30
PM3n
0
1
I/O mode selection of P3n pin (n = 0 to 6)
Output mode (output buffer on)
Input mode (output buffer off)
User’s Manual U14260EJ3V1UD
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