W65C22 Versatile Interface Adapter (VIA)
Introduction to the W65C22
The W65C22 (W65C22N and W65C22S) Versatile Interface Adapter (VIA) is a flexible I/O device for use with the 65xx series microprocessor family. The W65C22 includes functions for programmed control of two peripheral ports (Ports A and B). Two program controlled 8-bit bidirectional 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 line basis. Also provided are two programmable 16-bit Interval Timer/Counters with latches. Timer 1 may be operated in a One-Shot Interrupt Mode with interrupts on each count to zero, or in a Free-Run Mode with a continuous series of evenly spaced interrupts. Timer 2 functions as both an interval and pulse counter. Serial Data transfers are provided by a serial to parallel/parallel to serial shift register. Application versatility is further increased by various control registers, including an Interrupt Flag Register, an Interrupt Enable Register and two Function Control Registers.
Interface Signals Relationship
Features of the W65C22
- 2 x 8−bit, bi−directional peripheral I/O Ports
- 2 x 16−bit programmable Interval Timer/Counters
- Synchronous Serial bi−directional peripheral I/O Port
- Enhanced "Handshake" feature works with either 8− or
- Latched Input/Output Registers on both I/O Ports
- Programmable Data Direction Registers
- TTL compatible I/O peripheral lines
- 1.8V(W65C22S only) − 5V Power Supply
- Bus compatible with 14 MHz W65C02S and W65C816S
- Compatible with the 65xx and 68xx family of microprocessors
- Replacement for Rockwell / GTE / CMD / Synertek / MOS Technology NMOS 6522 and
CMOS 65C22 VIA's
- The W65C22S is lower power, faster and direct drive outputs with no current limiting resistors on outputs ports.
- The W65C22N is plug replacement of NMOS 6522 devices with current limiting resistors on output ports.
- The W65C22N does not have bus holding devices on the input, IO pins.
- The W65C22N IRQB is an open drain output that CAN be Wire-ORd, unlike the totem-pole output of the W65C22S (some customers have had to use a diode in series with the IRQB output when using the W65C22S in their systems that had Wire-ORd interrupts).