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 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.

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