8.4
Port 4
8.4.1
Overview
Port 4 is a 3-bit I/O port and 1-bit input port, configured as shown in figure 8-3.
Figure 8-3 Port 4 Pin Configuration
8.4.2
Register Configuration and Description
Table 8-8 shows the port 4 register configuration.
Table 8-8 Port 4 Registers
Name
Abbrev.
R/W
Initial Value
Address
Port data register 4
PDR4
R/W
H'F8
H'FFD7
Port control register 4
PCR4
W
H'F8
H'FFE7
1.
Port data register 4 (PDR4)
PDR4 is an 8-bit register that stores data for port 4 pins P4
2
to P4
0
. If port 4 is read while PCR4
bits are set to 1, the values stored in PDR4 are read, regardless of the actual pin states. If port 4 is
read while PCR4 bits are cleared to 0, the pin states are read.
Upon reset, PDR4 is initialized to H'F8.
Bit
Initial value
Read/Write
7
—
1
—
6
—
1
—
5
—
1
—
4
—
1
—
3
P4
1
R
0
P4
0
R/W
2
P4
0
R/W
1
P4
0
R/W
3
2
1
0
P4
P4
P4
P4
/IRQ
0
/TXD
32
/RXD
32
/SCK
32
3
2
1
0
Port 4
148