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7.5.2
Register Descriptions
Table 7.6 summarizes the registers of port 4.
Table 7.6
Port 4 Registers
Address*
Name
H'EE003
Port 4 data direction register
H'FFFD3
Port 4 data register
H'EE03E
Port 4 input pull-up MOS control
register
Note: * Lower 20 bits of the address in advanced mode.
Port 4 Data Direction Register (P4DDR): P4DDR is an 8-bit write-only register that can select
input or output for each pin in port 4.
Bit
P4 DDR
Initial value
Read/Write
• Modes 1 to 5 (Expanded Modes)
When all areas are designated as 8-bit-access areas by the bus controller's bus width control
register (ABWCR), selecting 8-bit bus mode, port 4 functions as an input/output port. In this
case, a pin in port 4 becomes an output port if the corresponding P4DDR bit is set to 1, and an
input port if this bit is cleared to 0.
When at least one area is designated as a 16-bit-access area, selecting 16-bit bus mode, port 4
functions as part of the data bus, regardless of the P4DDR settings.
• Modes 6 and 7 (Single-Chip Mode)
Port 4 functions as an input/output port. A pin in port 4 becomes an output port if the
corresponding P4DDR bit is set to 1, and an input port if this bit is cleared to 0.
P4DDR is a write-only register. Its value cannot be read. All bits return 1 when read.
P4DDR is initialized to H'00 by a reset and in hardware standby mode. In software standby mode
it retains its previous setting.
7
6
P4 DDR
P4 DDR
7
6
0
0
W
W
Abbreviation
P4DDR
P4DR
P4PCR
5
4
P4 DDR
P4 DDR
5
4
0
0
W
W
Port 4 data direction 7 to 0
These bits select input or output for port 4 pins
R/W
W
R/W
R/W
3
2
P4 DDR
P4 DDR
3
2
0
0
W
W
Initial Value
H'00
H'00
H'00
1
0
P4 DDR
1
0
0
0
W
W
175
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