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M38C88EA-XXXFP

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI ELECTRIC  

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MITSUBISHI MICROCOMPUTERS

38C8 Group

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

I/O PORTS

[Direction Registers]

The I/O ports P0–P3 and P41–P47 have direction registers which

determine the input/output direction of each individual pin. Each bit

in a direction register corresponds to one pin, each pin can be set to

be input port or output port.

When “0” is written to the bit corresponding to a pin, that pin be-

comes an input pin. When “1” is written to that bit, that pin becomes

an output pin.

If data is read from a pin set to output, the value of the port output

latch is read, not the value of the pin itself. Pins set to input are float-

ing. If a pin set to input is written to, only the port output latch is

written to and the pin remains floating.

Pull-up Control

By setting the PULL register A (address 001616) or the PULL register

B (address 001716), ports P0 to P4 except for port P40 can control

pull-up with a program.

However, the contents of PULL register A and PULL register B do not

affect ports programmed as the output ports.

b7

b0

PULL register A

(PULLA: address 001616)

P00–P03 pull-up

P04–P07 pull-up

P10–P13 pull-up

P14–P17 pull-up

P20–P23 pull-up

P24–P27 pull-up

P30–P33 pull-up

Not used (return “0” when read)

b7

b0

PULL register B

(PULLB: address 001716)

Not used (return “0” when read)

P41 pull-up

P42 pull-up

P43 pull-up

P44 pull-up

P45 pull-up

P46 pull-up

P47 pull-up

0: No pull-up

1: Pull-up

Note: The contents of PULL register A and PULL register B do

not affect ports programmed as the output port.

Fig. 10 Structure of PULL register A and PULL register B

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