4-66

CDP1871A,

CDP1871AC

CMOS Keyboard Encoder

Description

The CDP1871A is a keyboard encoder designed to

directly interface between a CDP1800-series micro-

processor and a mechanical keyboard array, providing

up to 53 ASCII coded keys and 32 HEX coded keys,

as shown in the system diagram (Figure 1).

The keyboard may consist of simple single-pole

single-throw (SPST) mechanical switches. Inputs are

provided for alpha-lock, control, and shift functions,

allowing 160 unique codes. An external R-C input is

available for user-selectable debounce times. The N-

key lock-out feature prevents unwanted key codes if

two or more keys are pressed simultaneously.

The CDP1871A and CDP1871AC are functionally

identical. They differ in that the CDP1871A has a

recommended operating voltage range of 4V to 10.5V,

and the CDP1871AC has a recommended operating

voltage range 4V to 6.5V. These types are supplied in

40 lead dual-in-line ceramic packages (D suffix), and

40 lead dual-in-line plastic packages (E suffix), and 44

lead plastic chip-carrier packages (Q suffix).

Features

• Directly Interfaces with CDP1800-Series Microprocessor

• Low Power Dissipation

• Three-State Outputs

• Scans and Generates Code for 53 Key ASCII Keyboard Plus

32 HEX Keys (SPST Mechanical Contact Switches)

• Shift, Control, and Alpha Lock Input

• RC-Controlled Debounce Circuitry

• Single Supply 4V to 10.5V . . . . . . . . . . . . . (CDP1871A)

4V to 6.5V . . . . . . . . . . . . . (CDP1871AC)

• N-Key Lockout

Ordering Information

PACKAGE

TEMP. RANGE

5V

10V

PKG.

NO.

PDIP

CDP1871ACE

CDP1871AE E40.6

PLCC

CDP1871ACQ

-

N44.65

SBDIP

CDP1871ACD

CDP1871AD D40.6

Burn-In

CDP1871ACDX

-

D40.6

REFERENCE APP NOTE 7374

August 1996

File Number

1374.2

Pinouts

40 LEAD PDIP, CERDIP

TOP VIEW

13

1

2

3

4

5

6

7

8

9

10

11

12

14

15

16

17

18

19

20

D1

D2

D3

D4

D5

D6

D7

D8

D9

D10

D11

S1

S2

S3

S4

S5

S6

S7

S8

28

40

39

38

37

36

35

34

33

32

31

30

29

27

26

25

24

23

22

21

SHIFT

CONTROL

ALPHA

DEBOUNCE

RTP

TPB

DA

BUS 7

BUS 6

BUS 5

BUS 4

BUS 3

BUS 2

BUS 1

BUS 0

CS4

CS3

CS2

CS1

44 LEAD PLCC

(Q Suffix) TOP VIEW

44 43 42 41 40

39

38

37

36

35

34

33

32

31

30

29

28

27

1

2

3

4

5

6

20 21 22 23 24 25 26

19

18

7

8

9

10

11

12

13

14

15

16

17

D5

D6

D7

D8

D9

D10

D11

S1

S2

S3

S4

RPT

TPB

DA

BUS 7

BUS 6

BUS 5

BUS 4

BUS 3

BUS 2

BUS 1

NC

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

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