WDC 65C21

The W65C21S is a very flexible Peripheral Interface Adapter (PIA) for use with WDC's 65xx and other 8-bit microprocessor families.

Peripheral device control is accomplished through two 8-bit bidirectional I/O Ports, with individually designed Data Direction Registers.

Data flow direction may be selected on a line-by-line basis with intermixed input and output lines within the same port.

This capability provides enhanced control over data transfer functions between the microprocessor and peripheral devices, as well as bidirectional data transfer between W65C21S Peripheral Interface Adapters in multiprocessor systems.

The PIA interfaces to the peripheral devices with four interrupt/control lines and two 8-bit bidirectional buses.