4-5

CDP1851,

CDP1851C

CMOS Programmable I/O Interface

Description

THE CDP1851 and CDP1851C are CMOS programmable two-

port I/Os designed for use as general-purpose I/O devices.

They are directly compatible with CDP1800-series micropro-

cessors functioning at maximum clock frequency. Each port

can be programmed in either byte-I/O or bit-programmable

modes for interfacing with peripheral devices such as printers

and keyboards.

Both ports A and B can be separately programmed to be 8-bit

input or output ports with handshaking control lines, RDY and

STROBE. Only port A can be programmed to be a bidirectional

port. This configuration provides a means for communicating

with a peripheral device or microprocessor system on a single

8-bit bus for both transmitting and receiving data. Handshaking

signals are provided to maintain proper bus access control.

Port A handshaking lines are used for input control and port B

handshaking lines are used for output; therefore port B must be

in the bit-programmable mode where handshaking is not used.

Ports A and B can be separately bit programmed so that each

individual line can be designated as an input or output line. The

handshaking lines may also be individually programmed as

input or output when port A is not in bidirectional mode.

The CDP1851 has a supply-voltage range of 4V to 10.5V, and

the CDP1851C has a range of 4V to 6.5V. Both types are sup-

plied in 40-lead dual-in-line plastic (E suffix) or hermetic

ceramic (D suffix) packages. The CDP1851C is also available

in chip form (H suffix).

Features

• 20 Programmable I/O Lines

• Programmable for Operation in Four Modes:

- Input

- Output

- Bidirectional

- Bit-programmable

• Operates in Either I/O or Memory Space

Ordering Information

PACKAGE TEMP. RANGE

5V

10V

PKG.

NO.

PDIP

CDP1851E

E40.6

Burn-In

CDP1851CEX

-

E40.6

SBDIP

-

D40.6

Burn-In

CDP1851CDX CDP1851DX D40.6

March 1997

File Number

1056.2

Pinout

CDP1851, CDP1851C

(PDIP, SBDIP)

TOP VIEW

13

1

2

3

4

5

6

7

8

9

10

11

12

14

15

16

17

18

19

20

CLOCK

CS

RA0

RA1

BUS0

BUS1

BUS2

BUS3

BUS4

BUS5

BUS6

BUS7

CLEAR

A INT

B INT

B RDY

B

B0

B1

28

40

39

38

37

36

35

34

33

32

31

30

29

27

26

25

24

23

22

21

RD/WE

WR/RE

TPB

A RDY

A

A0

A1

A2

A3

A4

A5

A6

A7

B7

B6

B5

B4

B3

B2

STROBE

STROBE

CDP1851 Programming Modes

MODE

(8)

PORT A

DATA PINS

(2)

PORT A

HANDSHAKING

PINS

(8)

PORT B

DATA PINS

(2)

PORT B

HANDSHAKING

PINS

Input

Accept Input

Data

READY, STROBE

Accept Input Data

READY, STROBE

Output

Output Data

READY, STROBE

Output Data

READY, STROBE

Bidirectional

(Port A Only)

Transfer In-

put/Output Data

Input Handshaking

for Port A

Must be Previous-

ly Set to Bit-Pro-

grammable Mode

Output Handshaking

for Port A

Bit-Program-

mable

Programmed In-

dividually as In-

puts or Outputs

Programmed Individ-

ually as Inputs or

Outputs

Programmed Indi-

vidually as Inputs

or Outputs

Programmed Individ-

ually as Inputs or

Outputs

CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.

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