_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ CMOS Perlph~rals
TERMINAL ASSIGNMENT
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TOP VIEW
9~CS~31926
4G-LEAO OIL PACKAGES
CDP1851, CDP1851C
CMOS Programmable 1/0 Interface
Features:
• 20 Programmable 110 Lines
• Programmable for Operation in Four Modes:
Input
Output
Bidirectional
Bit-programmable
• Operates in Either I/O or Memory Space
The RCA CDP1851 and CDP1851C are CMOS program-
mable two-port I/Os designed for use as general-purpose
1/0 devices. They are directly compatible with CDP1800
series microprocessors 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,
ROY 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 4 to 10.5 V, and
the CDP1851C has a range of 4 to 6.5 V Both types are
supplied in 40-lead dual-in-line plastic (E suffix) or hermetic
ceramic (0 suffix) packages. The CDP1851 C is also available
in chip form (H suffix).
CDP1851 Progrsmmlng Modes
Mode
Input
Output
Bidrectional
(Port A only)
(8)
PortA
Dala Pins
Accept input data
Output data
Transfer input!
output data
Bit-
Programmable
Programmed
individually as
inputs or outputs
(2)
PortA
Handshaking Pins
READY, STROBE
READY, STROBE
Input handshaking
for Port A
Programmed
individually as
inputs or outputs
(8)
Port B
Dala Pins
Accept input data
Output data
Must be
previously set to
bit-programmable mode
Programmed
individually as
inputs or outputs
(2)
Port B
Handshaking Pins
READY, STROBE
READY, STROBE
Output handshaking
for Port A
Programmed
individually as
inputs or outputs
File Number 1056
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