CDP1871A,
CDP1871AC
REFERENCE APP NOTE 7374
August 1996
CMOS Keyboard Encoder
Features
Description
• Directly Interfaces with CDP1800-Series Microprocessor
• Low Power Dissipation
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).
• Three-State Outputs
• Scans and Generates Code for 53 Key ASCII Keyboard Plus
32 HEX Keys (SPST Mechanical Contact Switches)
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.
• 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
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).
Ordering Information
PKG.
NO.
PACKAGE TEMP. RANGE
5V
10V
o
o
PDIP
-40 C to +85 C CDP1871ACE CDP1871AE E40.6
o
o
PLCC
SBDIP
-40 C to +85 C CDP1871ACQ
-
N44.65
-40 C to +85 C CDP1871ACD CDP1871AD D40.6
CDP1871ACDX D40.6
o
o
Burn-In
-
Pinouts
44 LEAD PLCC
40 LEAD PDIP, CERDIP
TOP VIEW
(Q Suffix) TOP VIEW
D1
1
2
3
4
5
6
7
8
9
40 VDD
D2
D3
D4
D5
D6
D7
D8
D9
39 SHIFT
38 CONTROL
37 ALPHA
36 DEBOUNCE
35 RTP
6
5
4
3
2
1
44 43 42 41 40
D5
D6
D7
D8
D9
D10
D11
S1
7
39
38
37
36
35
34
33
32
31
30
29
RPT
8
TPB
34 TPB
9
DA
33 DA
10
11
12
13
14
15
16
17
BUS 7
BUS 6
BUS 5
BUS 4
BUS 3
BUS 2
BUS 1
NC
32 BUS 7
31 BUS 6
30 BUS 5
29 BUS 4
28 BUS 3
27 BUS 2
26 BUS 1
25 BUS 0
24 CS4
D10 10
D11 11
S1 12
S2 13
S3 14
S4 15
S5 16
S6 17
S7 18
S8 19
VSS 20
S2
S3
S4
18 19 20 21 22 23 24 25 26 27 28
23 CS3
22 CS2
21 CS1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
File Number 1374.2
http://www.intersil.com or 407-727-9207 | Copyright © Intersil Corporation 1999
4-66