Commodore PET 2001-8 user port pinout

The Commodore PET 2001-8 user port exposes eight individually programmable parallel I/O lines and handshake signals from the 6522 VIA.

24-contact user port

24 contacts Current package

Commodore · 12 positions × 2 sides · keyed PCB edge

24-contact user port pinout

Diagram rotated to show both contact rows. Numbers are the upper side. Letters are the lower side. Match the keyed connector to the rear view in the manual.

Selected pin details

M · CB2

Programmable I/O · Bidirectional

VIA handshake or shift-register signal.

Commodore PET 2001-8 User Manual, October 1978, Tables 7.6–7.7

Electrical limits · Link to this pin

All 24 pins

Pin	Signal	Direction	Function
1	GND Return	Return	Digital ground. Use this reference for a logic measurement.
2	Video Diagnostic output	Diagnostic output	Raw video from the logic board. Use the documented display interface.
3	IEEE-SRQ Diagnostic contact	Diagnostic contact	Connected to the IEEE-488 service request line.
4	IEEE-EOI Diagnostic contact	Diagnostic contact	Connected to the IEEE-488 end-or-identify line.
5	Diagnostic Sense Input	Input	Pulling low at boot enters the built-in diagnostic routine. Leave open for a normal startup.
6	Tape 1 Read Diagnostic contact	Diagnostic contact	Read signal for the first cassette interface.
7	Tape 2 Read Diagnostic contact	Diagnostic contact	Read signal for the second cassette interface.
8	Tape Write Diagnostic contact	Diagnostic contact	Write signal for the cassette interfaces.
9	Vertical sync Diagnostic output	Diagnostic output	Raw display vertical timing signal.
10	Horizontal sync Diagnostic output	Diagnostic output	Raw display horizontal timing signal.
11	GND Return	Return	Digital ground. Use this reference for a logic measurement.
12	GND Return	Return	Digital ground. Use this reference for a logic measurement.
A	GND Return	Return	Digital ground. Use this reference for a logic measurement.
B	CA1 Handshake input	Handshake input	Edge-sensitive input of the 6522 VIA.
C	PA0 Programmable I/O	Programmable I/O	6522 VIA parallel data bit. Select its direction in the data direction register.
D	PA1 Programmable I/O	Programmable I/O	6522 VIA parallel data bit. Select its direction in the data direction register.
E	PA2 Programmable I/O	Programmable I/O	6522 VIA parallel data bit. Select its direction in the data direction register.
F	PA3 Programmable I/O	Programmable I/O	6522 VIA parallel data bit. Select its direction in the data direction register.
H	PA4 Programmable I/O	Programmable I/O	6522 VIA parallel data bit. Select its direction in the data direction register.
J	PA5 Programmable I/O	Programmable I/O	6522 VIA parallel data bit. Select its direction in the data direction register.
K	PA6 Programmable I/O	Programmable I/O	6522 VIA parallel data bit. Select its direction in the data direction register.
L	PA7 Programmable I/O	Programmable I/O	6522 VIA parallel data bit. Select its direction in the data direction register.
M	CB2 Programmable I/O	Programmable I/O	VIA handshake or shift-register signal.
N	GND Return	Return	Digital ground. Use this reference for a logic measurement.

Signal assignments

Eight-bit parallel port

Set each pin’s direction using the 6522 VIA data direction register. Use an input-only instrument for the first measurement.

Electrical limits

Parameter	Limit	Conditions and source
Parallel port controller6522 VIA	6522 VIA	The measured signal is PA0 at contact C. Commodore PET 2001-8 User Manual, October 1978, Tables 7.6–7.7
Bench loadHigh impedance only	High impedance only	Use a 10× passive scope probe. The example draws no supply current from the connector. Measurement fixture design

Models and documents

The map covers the external 24-contact user port. The signal roles and supply contacts are specific to the PET 2001-8 shown in the manufacturer guide.

PET 2001-8: User-port connector in the cited manufacturer documentation.

Commodore PET 2001-8 user manual· Manufacturer manual, October 1978, pp. 59–62.