UPD78C18 datasheet(22/110 Pages) NEC

22 / 110 page

µPD78C17,78C18

2.5

PORT FUNCTIONS

(1)

PA7 to PA0 (PORT A)

This is an 8-bit input/output port which has input/output buffer and output latch functions. Port A can

be set as to input or output bit-wise using the MODE A register. And

µPD78C18 port A pull-up resistor

specification is performed bit-wise by mask option.

Port A is set as follows when setting the input port or after reset.

High-impedance : Without pull-up resistor

High level

: With pull-up resistor

Fig. 2-5 Port A

(a)

When specified as output port (MAn = 0)

The output latch is effective, enabling data exchange by a transfer instruction between the output latch

and the accumulator. Direct bit setting/resetting of output latch contents is possible by an arithmetic or

logical operation instruction without the use of an accumulator. Once data is written to the output latch,

the data is held until a port A manipulation instruction is executed or the data is reset.

Fig. 2-6 Port A Specified as Output Port

Note Only

µPD78C18

V DD

MAn

Latch

WRM

Output

Latch

WRP

RDO

RDI

Output

Buffer

Mask OptionNote

PAn

V DD

Output

Latch

WRP

RDO

Mask OptionNote

PAn

Note Only

µPD78C18

UPD78C18 Datasheet(PDF) 22 Page - NEC

UPD78C18 Datasheet(HTML) 22 Page - NEC

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