HD6475328-CP10 HITACHI [Hitachi Semiconductor], HD6475328-CP10 Datasheet - Page 172

• Manufacturer Part Number: HD6475328-CP10
• Description: original Hitachi CMOS microcomputer unit (MCU)
• Manufacturer: HITACHI [Hitachi Semiconductor]

9.5.2 Port 4 Registers
Register Configuration: Table 9-7 lists the registers of port 4.
Table 9-7 Port 4 Registers
Name
Port 4 data direction register
Port 4 data register
1. Port 4 Data Direction Register (P4DDR)—H'FF85
Bit
Initial value
Read/Write
P4DDR is an 8-bit register that selects the direction of each pin in port 4.
P4DDR can be written but not read. An attempt to read this register does not cause an error, but
all bits are read as “1,” regardless of their true values.
At a reset and in the hardware standby mode, P4DDR is initialized to H'00, making all eight pins
input pins. P4DDR is not initialized in the software standby mode, so if a P4DDR bit is set to “1”
when the chip enters the software standby mode, the corresponding pin continues to output the
value in the port 4 data register.
Single-Chip Mode: A pin functions as an output pin if the corresponding bit in P4DDR is set
to “1,” and as in input pin if the bit is cleared to “0.”
Expanded Modes: All bits of P4DDR are fixed at “1” and cannot be modified.
P4
7
W
7
0
DDR P4
6
W
6
DDR P4
0
Abbreviation
P4DDR
P4DR
5
W
5
DDR P4
0
155
4
W
4
0
DDR P4
Read/Write
W
R/W
3
W
3
DDR P4
0
Initial Value
H'00
H'00
2
W
2
0
DDR P4
1
W
1
0
DDR P4
Address
H'FF85
H'FF87
0
W
0
DDR
0