6522 VIA pinout

DIP-40. Two 8-bit ports, timers, serial and user port

Versatile interface adapter. Two ports (PA, PB), two timers, shift register and handshake lines CA1/CA2 and CB1/CB2. VIC-20: VIA1 at $9110 (serial bus, cassette, RESTORE NMI), VIA2 at $9120 (keyboard, joystick, timers, IRQ). PET: VIA at $E840 (user port, cassette 2, IEEE-488 handshake, timers, CB2 beep).

Open the interactive VIA pinout

Pins

Pin	Name	Type	Signal
1	Vss	ground	0 V.
2	PA0	io	Port A bit 0.
3	PA1	io	Port A bit 1.
4	PA2	io	Port A bit 2.
5	PA3	io	Port A bit 3.
6	PA4	io	Port A bit 4.
7	PA5	io	Port A bit 5.
8	PA6	io	Port A bit 6.
9	PA7	io	Port A bit 7.
10	PB0	io	Port B bit 0.
11	PB1	io	Port B bit 1.
12	PB2	io	Port B bit 2.
13	PB3	io	Port B bit 3.
14	PB4	io	Port B bit 4.
15	PB5	io	Port B bit 5.
16	PB6	io	Port B bit 6.
17	PB7	io	Port B bit 7.
18	CB1	io	Handshake / shift clock, port B.
19	CB2	io	Handshake / shift data, port B (board use: see the summary).
20	Vcc	power	+5 V supply.
21	/IRQ	ctrl	Interrupt request to the CPU /IRQ.
22	R/W	ctrl	Read/write from the CPU.
23	/CS2	ctrl	Chip select 2, active LOW.
24	CS1	ctrl	Chip select 1, active HIGH.
25	Φ2	clock	Phase 2 clock from the CPU.
26	D7	data	Data bus bit 7.
27	D6	data	Data bus bit 6.
28	D5	data	Data bus bit 5.
29	D4	data	Data bus bit 4.
30	D3	data	Data bus bit 3.
31	D2	data	Data bus bit 2.
32	D1	data	Data bus bit 1.
33	D0	data	Data bus bit 0.
34	/RES	ctrl	Reset. LOW clears the VIA.
35	RS3	addr	Register select bit 3.
36	RS2	addr	Register select bit 2.
37	RS1	addr	Register select bit 1.
38	RS0	addr	Register select bit 0.
39	CA2	io	Handshake line, port A.
40	CA1	io	Interrupt input, port A.

Fitted in

VIC-20 UAB1, UAB3
PET / CBM
Commodore 1541 disk drive Serial VIA ($1800): UAB1 long board, UC3 short boards, U6 1541-II. Disk VIA ($1C00): UC4 long board, UC2 short boards, U8 1541-II. 1541C: UC1 and UC3
Commodore 1571 disk drive U9 serial ($1800), U4 disk ($1C00); 65C22A CMOS parts
BBC Micro Model B IC3 (system VIA), IC69 (user VIA)
BBC Master 128 IC8 (system VIA), IC6 (user VIA)
Oric-1 IC6 (6522A)
Oric Atmos IC6 (same numbering per the Oric/Atmos checklist; verify)

Sources

MOS MCS6522 VIA data sheet, p. 1 pin configuration (GIF scans)