Chips › I/O & support › Parallel I/O (PIA/VIA/PPI) › MOS 6522 VIA
MOS 6522 VIA
1977
MOS Technology's Versatile Interface Adapter, offering parallel ports, timers and a shift register for 6502-based systems.
Machines
Reference & documentation
External technical references for programming MOS 6522 VIA and for writing emulators.
| Resource | Type | Notes |
|---|---|---|
| MOS 6522 Preliminary Datasheet (Nov 1977) ↗ | Datasheet | Original MOS spec: registers, timers, timing diagrams |
| WDC W65C22S VIA Datasheet (2004) ↗ | Datasheet | Modern CMOS variant; detailed electrical and timing specs |
| 6522 Interrupt Sources & Priority ↗ | Interrupt list | Seven IFR sources; bit-scan priority ordering |
| 6522 VIA Register Reference (zimmers) ↗ | Memory map | All 16 registers, addresses and bit meanings |
| MOS 6522 Datasheet - Pinout & Signals ↗ | Pinout | 40-pin package, port and control-line signals |
| 6522 VIA Programming Guide (zimmers) ↗ | Programming | Latching, handshake, timer and shift-register modes |
| Investigating Interrupts (6502.org tutorial) ↗ | Programming | IFR/IER setup with timer ISR examples |
| 6522 VIA Emulation Discrepancies (stardot) ↗ | Reference | Hardware-tested timer and IRQ cycle edge cases |
| MOS Technology 6522 - Wikipedia ↗ | Reference | Overview of ports, timers, shift register, known bugs |
| 6522 Interrupt Identification (6502.org) ↗ | Source | Assembly routine identifying the seven interrupt sources |
| 6522 ACR Writes vs Timer IRQ (stardot) ↗ | Test suite | Real-hardware regression tests for emulator conformance |