2. Port control register 4 (PCR4)
Bit
7
—
1
6
—
1
5
—
1
4
—
1
3
—
1
2
1
0
PCR42 PCR41 PCR40
Initial value
Read/Write
0
0
0
—
—
—
—
—
W
W
W
PCR4 is an 8-bit register for controlling whether each of port 4 pins P42 to P40 functions as an
input pin or output pin. Setting a PCR4 bit to 1 makes the corresponding pin an output pin, while
clearing the bit to 0 makes the pin an input pin. PCR4 and PDR4 settings are valid when the
corresponding pins are designated for general-purpose input/output by SCR3-2.
Upon reset, PCR4 is initialized to H'F8.
PCR4 is a write-only register, which always reads all 1s.
8.5.3
Pin Functions
Table 8-12 shows the port 4 pin functions.
Table 8-12 Port 4 Pin Functions
Pin
Pin Functions and Selection Method
The pin function depends on bit IRQ0 in PMR3.
P43/IRQ0
IRQ0
0
1
Pin function
P43 input pin
IRQ0 input pin
P42/TXD32
The pin function depends on bit TE in SCR3-2, bit SPC32 in SPCR, and bit
PCR42 in PCR4.
SPC32
TE
0
0
1
1
PCR42
0
1
*
Pin function
P42 input pin
P42 output pin
TXD32 output pin
P41/RXD32
The pin function depends on bit RE in SCR3-2 and bit PCR41 in PCR4.
RE
0
1
PCR41
0
1
*
Pin function
P41 input pin
P41 output pin
RXD32 input pin
*: Don’t care
153
ETC [ ETC ]
