CDP1851

THE CDP1851 and CDP1851C are CMOS programmable twoport I/Os designed for use as general-purpose I/O 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, 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 supplied 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).