Interactive Connector Diagram
Click or tap any pin in the diagram below to inspect its signal assignment, electrical specification, and wire colour standard.
Used in Retro Machine Hubs
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Connector Specifications
Full Pin Assignment & Wiring Reference
| Pin | Signal Name | Direction | Electrical Spec / Role | Wire Colour / SCART / Adapter Target |
|---|---|---|---|---|
| Top 1 / GPIB 1 | /DIO1 (Data Bit 0) | I/O | IEEE-488 Data Bit 0 (Active-Low via MC3446 to PIA2 PA0/PB0) | GPIB Pin 1 |
| Top 2 / GPIB 2 | /DIO2 (Data Bit 1) | I/O | IEEE-488 Data Bit 1 | GPIB Pin 2 |
| Top 3 / GPIB 3 | /DIO3 (Data Bit 2) | I/O | IEEE-488 Data Bit 2 | GPIB Pin 3 |
| Top 4 / GPIB 4 | /DIO4 (Data Bit 3) | I/O | IEEE-488 Data Bit 3 | GPIB Pin 4 |
| Top 5 / GPIB 5 | /EOI (End/Identify) | I/O | End Or Identify control line (PIA1 CA2) | GPIB Pin 5 |
| Top 6 / GPIB 6 | /DAV (Data Valid) | I/O | Data Valid handshake strobe (PIA2 CA2 / CB1) | GPIB Pin 6 |
| Top 7 / GPIB 7 | /NRFD (Not Ready) | I/O | Not Ready For Data handshake line (VIA PB1 / CA1) | GPIB Pin 7 |
| Top 8 / GPIB 8 | /NDAC (Not Accepted) | I/O | No Data Accepted handshake line (VIA PB0 / PIA2 CA1) | GPIB Pin 8 |
| Top 9 / GPIB 9 | /IFC (Interface Clr) | Out | Interface Clear / Bus Reset output | GPIB Pin 9 |
| Top 10 / GPIB 10 | /SRQ (Service Req) | In | Service Request interrupt line | GPIB Pin 10 |
| Top 11 / GPIB 11 | /ATN (Attention) | Out | Attention command mode select (VIA PB2) | GPIB Pin 11 |
| Top 12 / GPIB 12 | SHIELD GND | GND | Cable Shield Ground | GPIB Pin 12 |
| Bot A–D / GPIB 13–16 | /DIO5 – /DIO8 | I/O | A (13)=/DIO5 (Bit 4), B (14)=/DIO6 (Bit 5), C (15)=/DIO7 (Bit 6), D (16)=/DIO8 (Bit 7) | GPIB Pins 13–16 |
| Bot E–N / GPIB 17–24 | /REN (E) & GNDs (F–N) | GND | E (17)=/REN (tied to GND on PET); F, H, J, K, L, M, N (18–24) = Signal Grounds! | GPIB Pins 17–24 (GND) |
Building a PET Edge-to-GPIB Cable & Using PETdisk MAX
Unlike the VIC-20 and C64 (which serialized the IEEE-488 bus into the slow 6-pin IEC bus to save cable cost), every Commodore PET uses a true 8-bit parallel IEEE-488 (GPIB) bus (J1 on the rear-left of the PET PCB) capable of transferring disk data 5x to 10x faster than a C64 1541! Note that while HP/IEEE instruments use a 24-pin stackable ribbon connector where Pins 1–12 are one row and Pins 13–24 are the bottom row, the PET motherboard uses a 2x12 PCB edge finger (Top 1–12 = IEEE Pins 1–12; Bottom A–N = IEEE Pins 13–24).
- PET Edge-to-IEEE-488 Cable (CBM 320101): Map Top Row Pins 1–12 directly to IEEE-488 Ribbon Pins 1–12, and map Bottom Row Letters A, B, C, D, E, F, H, J, K, L, M, N in order to IEEE-488 Ribbon Pins 13–24!
- Powering a PETdisk MAX / SD2PET: Because the IEEE-488 bus carries no +5 V power pin, modern SD card drives like the PETdisk MAX tap +5 V from the adjacent Datasette (J3 Pin B/2) or User Port (J2).