W65C21S Description
The WDC W65C21S is a very flexible Peripheral Interface Adapter (PIA) for use with WDC’s 65xx and other 8-bit microprocessor families. The W65C21S provides programmed microprocessor control of up to two peripheral devices (Port A and Port B). Peripheral device control is acplished through two 8-bit bidirectional I/O Ports, with individually designed Data Direction Registers.