H8SLASH3003 datasheet(259/715 Pages) RENESAS

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9.2.2 Register Descriptions

Table 9-2 summarizes the registers of port 4.

Table 9-2 Port 4 Registers

Address*

Name

Abbreviation

R/W

Initial Value

H'FFC5

Port 4 data direction register

P4DDR

H'00

H'FFC7

Port 4 data register

P4DR

R/W

H'00

H'FFDA

Port 4 input pull-up control register

P4PCR

R/W

H'00

Note: * Lower 16 bits of the address.

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.

8-Bit Bus Mode: When all areas are designated as 8-bit-access areas, selecting 8-bit bus mode,

port 4 functions as a generic input/output port. A pin in port 4 becomes an output pin if the

corresponding P4DDR bit is set to 1, and an input pin if this bit is cleared to 0.

16-Bit Bus Mode: When at least one area is designated as a 16-bit-access area, selecting 16-bit

bus mode, port 4 functions as the lower data bus.

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. When port 4 functions as a

generic input/output port, if a P4DDR bit is set to 1, the corresponding pin maintains its output

state in software standby mode.

Bit

Initial value

Read/Write

P4 DDR

Port 4 data direction 7 to 0

These bits select input or output for port 4 pins

P4 DDR

241

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