82C55 datasheet(13/23 Pages) INTERSIL

13 / 23 page

982

HS-82C55ARH

Control Word will always be in the format illustrated in Figure

11 with Bit D7 high to indicate Control Word Mode Informa-

tion.

FIGURE 10. BASIC MODE DEFINITIONS & BUS INTERFACE

TABLE 1.

INPUT OPERATION

(READ)

00010

Port A - Data Bus

01010

Port B - Data Bus

10010

Port C - Data Bus

11010

Control Word - Data Bus

TABLE 2.

OUTPUT OPERATION

(WRITE)

00100

Data Bus - Port A

01100

Data Bus - Port B

10100

Data Bus - Port C

11100

Data Bus - Control Word

RD, WR

D7 - D0

A0 - A1

BCA

I/O

PB7 - PB0 PC3 - PC0 PC7 - PC4 PA7 - PA0

MODE 0

DATA BUS

CONTROL BUS

ADDRESS BUS

BCA

I/O

PB7 - PB0

PA7 - PA0

MODE 1

CONTROL

OR I/O

CONTROL

OR I/O

BCA

I/O

BIDIREC-

PB7 - PB0

PA7 - PA0

MODE 2

I/O

CONTROL

TIONAL

FIGURE 11. MODE SET CONTROL WORD FORMAT

Mode Selection

There are three basic modes of operation that can be

selected by the system software:

When the RESET input goes “high”, all ports will be set to

the input mode with all 24 port lines held at the logic “one”

level by internal bus hold devices. After reset, the HS-

82C55ARH can remain in the input mode with no additional

initialization required. This eliminates the need for pullup or

pulldown resistors in all CMOS designs. During the

execution of the system program, any of the other modes

may be selected using a single output instruction. This

allows a single HS-82C55ARH to service a variety of

peripheral devices with a simple software maintenance

routine.

The modes for Port A and Port B can be separately deﬁned

while Port C is divided into two portions as required by the

Port A and Port B deﬁnitions. All of the output registers,

including the status register, will be reset whenever the

mode is changed. Modes may be combined so that their

functional deﬁnition can be “tailored” to almost any I/O struc-

ture. For instance: Group B can be programmed in Mode 0

to monitor simple switch closings or display computational

results, Group A could be programmed in Mode 1 to monitor

a keyboard or tape recorder on an interrupt-driven basis.

TABLE 3.

DISABLE FUNCTION

XXXX

Data Bus - 3-State

Mode 0 - Basic Input/Output

Mode 1 - Strobed Input/Output

Mode 2 - Bidirectional Bus

D7 D6 D5 D4 D3 D2 D1 D0

CONTROL WORD

GROUP B

PORT C (LOWER)

1 = INPUT

0 = OUTPUT

PORT B

1 = INPUT

0 = OUTPUT

MODE SELECTION

0 = MODE 0

1 = MODE 1

GROUP A

PORT C (UPPER)

1 = INPUT

0 = OUTPUT

PORT A

1 = INPUT

0 = OUTPUT

MODE SELECTION

00 = MODE 0

01 = MODE 1

1X = MODE 2

MODE SET FLAG

1 = ACTIVE

Spec Number

518060

82C55 Datasheet(PDF) 13 Page - Intersil Corporation

82C55 Datasheet(HTML) 13 Page - Intersil Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Datasheet Download

Link URL