
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
-40
o
C to +85
o
C CDP1851CE
CDP1851E
E40.6
Burn-In
CDP1851CEX
-
E40.6
SBDIP
-40
o
C to +85
o
C CDP1851CD
-
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
V
SS
28
40
39
38
37
36
35
34
33
32
31
30
29
27
26
25
24
23
22
21
V
DD
RD/WE
WR/RE
TPB
A RDY
A
A0
A1
A2
A3
A4
A5
A6
A7
B7
B6
B5
B4
B3
B2
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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Intersil Corporation 1999