WDC 65C22

The W65C22 versatile interface adapter (VIA) is an input/output device for use with the 65xx series microprocessor family. Overview Designed by the Western Design Center, the W65C22 is made in two versions, both of which are rated for 14 megahertz operation, and available in DIP-40 or PLCC-44 packages. W65C22N: This device is fully compatible with the NMOS 6522 produced by MOS Technology and others, and includes current-limiting resistors on its output lines. The W65C22N has an open-drain interrupt output (the pin) that is compatible with a wired-OR interrupt circuit. Hence the DIP-40 version is a "drop-in" replacement for the NMOS part. W65C22S: This device is fully software– and partially hardware–compatible with the NMOS part. The W65C22S' output is a totem pole configuration, and thus cannot be directly connected to a wired-OR interrupt circuit. As with the NMOS 6522, the W65C22 includes functions for programmed control of two peripheral ports (ports A and B). Two program–controlled 8-bit bi-directional peripheral I/O ports allow direct interfacing between the microprocessor and selected peripheral units. Each port has input data latching capability. Two programmable data direction registers (A and B) allow selection of data direction (input or output) on an individual I/O line basis.