82C55 datasheet(21/23 Pages) INTERSIL

21 / 23 page

990

HS-82C55ARH

Current Drive Capability

Any output on Port A, B or C can sink or source 2.5mA. This

feature allows the 82C55A to directly drive Darlington type

drivers and high-voltage displays that require such sink or

source current.

Reading Port C Status (Figures 23 and 24)

In Mode 0, Port C transfers data to or from the peripheral

device. When the 82C55A is programmed to function in

Modes 1 or 2, Port C generates or accepts “hand shaking”

signals with the peripheral device. Reading the contents of

Port C allows the programmer to test or verify the “status” of

each peripheral device and change the program ﬂow

accordingly.

There is no special instruction to read the status information

from Port C. A normal read operation of Port C is executed

to perform this function.

FIGURE 25. INTERRUPT ENABLE FLAGS IN MODES 1 AND 2

INTERRUPT

ENABLE FLAG*

POSITION

ALTERNATE PORT C

PIN SIGNAL (MODE)

INTE B

PC2

ACKB (Output Mode 1) or

STBB (Input Mode 1)

INTE A2

PC4

STBA (Input Mode 1 or

Mode 2)

INTE A1

PC6

ACKA (Output Mode 1 or

Mode 2)

Spec Number

518060

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