Port 3 Operating Modes - NEC PD78212 User Manual

(a) Port mode
If a port is put in a port mode by the PMC3 register, the port mode register (PM3) can put each bit of the port
in either the input or output mode independently of the other bits.
(b) Control signal I/O mode
The PMC3 register can specify each pin of port 3 as a control pin independently of the other pins, as described
below.
(i) RxD (receive data)
The RxD pin receives serial data from the asynchronous serial interface.
(ii) TxD (transmit data)
The TxD pin outputs serial data to the asynchronous serial interface.
(iii) SCK (serial clock)
The SCK pin is a serial clock I/O pin for the clock-synchronized serial interface.
(iv) SO (serial output)/SB0 (serial bus)
The SO pin outputs serial data (during three-wire serial I/O mode). The SB0 pin is a serial bus I/O pin
(during the SBI mode).
Remark For bit 3 (P33) of port 3, "SB0" is a reserved word in the NEC assembly program package. The bit is also defined in a header
file named sfrbit.h by the C compiler.
(v) TO0 through TO3 (timer output)
The TO0 through TO3 pins are timer output pins.
Table 5-4 Port 3 Operating Modes (n = 0 through 7)
Mode Port mode
Condition PMC3n = 0
P30
P31
P32
P33
I/O port
P34
P35
P36
P37
Chapter 5 Port Functions
Control signal I/O mode
PMC3n = 1
RxD input
TxD output
SCK I/O
SO output or SB0 I/O
TO0 output
TO1 output
TO2 output
TO3 output
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