CHAPTER 2 PIN FUNCTIONS
39
User’s Manual U11302EJ4V0UM
2.2.3 P20 to P27 (Port 2)
These pins constitute an 8-bit I/O port. Besides serving as I/O port pins, they function as serial interface data I/
O, clock I/O, automatic transmit/receive busy input, and strobe output pins.
The following operating modes can be specified in 1-bit units.
(1) Port mode
P20 to P27 function as an 8-bit I/O port. They can be specified in input or output mode in 1-bit units using port
mode register 2 (PM2). When they are used as input port pins, an on-chip pull-up resistor can be used by setting
the pull-up resistor option register (PUO).
(2) Control mode
P20 to P27 function as serial interface data I/O, clock I/O, automatic transmit/receive busy input, and strobe output
pins.
(a) SI0, SI1, SO0, SO1
Serial interface serial data I/O pins
(b) SCK0 and SCK1
Serial interface serial clock I/O pins
(c) SB0 and SB1
NEC Electronics standard serial bus interface I/O pins
(d) BUSY
Serial interface automatic transmit/receive busy input pin
(e) STB
Serial interface automatic transmit/receive strobe output pin
Caution If port 2 is used as serial interface pins, the I/O and output latches must be set according
to the function. For the setting method, refer to Figure 13-3 Format of Serial Operating
Mode Register 0 and Figure 14-3 Format of Serial Operating Mode Register 1.
2.2.4 P30 to P37 (Port 3)
These pins constitute an 8-bit I/O port. Besides serving as I/O port pins, they function as timer I/O, clock output,
and buzzer output pins.
In mask ROM versions, use of pull-down resistors can be specified with the mask option.
Port 3 can drive LEDs directly.
The following operating modes can be specified in 1-bit units.
(1) Port mode
P30 to P37 function as an 8-bit I/O port. They can be specified in input or output mode in 1-bit units using port
mode register 3 (PM3). When they are used as input port pins, an on-chip pull-up resistor can be used by setting
the pull-up resistor option register (PUO).
Содержание mPD780208 Subseries
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