HD64F3028F25 Datasheet, PDF (292/925 Pages) Renesas Technology Corp – Hardware Manual Renesas 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Series

8.5.2 Register Descriptions
Table 8.6 summarizes the registers of port 4.
Table 8.6 Port 4 Registers
Address^*
Name
Abbreviation R/W
H'EE003
Port 4 data direction register
P4DDR
W
H'FFFD3
Port 4 data register
P4DR
R/W
H'EE03E
Port 4 input pull-up control register P4PCR
R/W
Note: * Lower 20 bits of the address in advanced mode.
Initial Value
H'00
H'00
H'00
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
Initial value
Read/Write
7
6
5
4
3
2
1
0
P4₇DDR P4₆DDR P4₅DDR P4₄DDR P4₃DDR P4₂DDR P4₁DDR P4₀DDR
0
0
0
0
0
0
0
0
W
W
W
W
W
W
W
W
Port 4 data direction 7 to 0
These bits select input or output for port 4 pins
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.
ABWCR and P4DDR are not initialized in software standby mode. Therefore, if a transition is
made to software standby mode while port 4 is functioning as an input/output port and a P4DDR
bit is set to 1, the corresponding pin maintains its output state.
Rev. 2.00, 09/03, page 260 of 890