25 PIN D-SUB MALE at the Amiga 1000
The Amiga 1000 parallel port is a 25-pin D-type male connector providing a nominally Centronics-compatible 8-bit bidirectional parallel interface, primarily intended for printer use. Unlike the later A500, A2000, and A3000, which use a female DB25, the A1000 uses a male DB25 and differs in two critical signal assignments: pin 1 carries DRDY* (data-ready, active low) rather than STROBE*, and pin 23 carries +5 V rather than ground. The eight data lines (D0–D7) connect to CIA-A port B of the Amiga’s custom chip set and are fully bidirectional; handshaking is performed by a two-line asynchronous protocol using DRDY* and ACK*. Standard parallel printer cables designed for PC or later-model Amiga use must not be connected to the A1000 without an adapter, as doing so will short pin 23 and may damage the computer.
| Pin | Name | Dir | Description |
|---|---|---|---|
| 1 | /STROBE | OUT | Strobe |
| 2 | D0 | IN/OUT | Data Bit 0 |
| 3 | D1 | IN/OUT | Data Bit 1 |
| 4 | D2 | IN/OUT | Data Bit 2 |
| 5 | D3 | IN/OUT | Data Bit 3 |
| 6 | D4 | IN/OUT | Data Bit 4 |
| 7 | D5 | IN/OUT | Data Bit 5 |
| 8 | D6 | IN/OUT | Data Bit 6 |
| 9 | D7 | IN/OUT | Data Bit 7 |
| 10 | /ACK | IN | Acknowledge |
| 11 | BUSY | IN/OUT | Busy |
| 12 | POUT | IN/OUT | Paper Out |
| 13 | SEL | IN/OUT | Select (Shared with RS232 RING-indicator) |
| 14 | GND | - | Signal Ground |
| 15 | GND | - | Signal Ground |
| 16 | GND | - | Signal Ground |
| 17 | GND | - | Signal Ground |
| 18 | GND | - | Signal Ground |
| 19 | GND | - | Signal Ground |
| 20 | GND | - | Signal Ground |
| 21 | GND | - | Signal Ground |
| 22 | GND | - | Signal Ground |
| 23 | +5V | OUT | +5 Volts DC (10 mA max) |
| 24 | n/c | - | Not connected. |
| 25 | /RESET | OUT | Reset |
Notes
- Direction is Computer relative Peripheral.
- The connector on the A1000 is DB25 male (pins protruding), in contrast to the DB25 female used on the A500, A2000, and A3000.
- Pin 23 supplies +5 V (up to 10 mA) on the A1000. On standard PC parallel cables and later Amiga cables, pin 23 is ground. Connecting such a cable directly to the A1000 will short +5 V to ground and can damage the machine.
- Pin 1 on the A1000 is labelled DRDY* (data-ready, active low) in the original hardware reference manual; the signal name /STROBE in the table above reflects the table as published on this page. The DRDY*/ACK* two-line asynchronous handshake differs from the STROBE*/BUSY handshake used on later Amigas and standard Centronics printers.
- The parallel interface is described in the original documentation as “similar to Centronics, but the pin assignment and drive characteristics vary significantly from that specification.”
- Pin 25 carries RESET* (system reset output), present on the A1000 only.
Signals
- /STROBE (DRDY*) — data-ready strobe output (active low); asserted by the host to indicate valid data on the data lines
- D0–D7 — eight bidirectional data lines controlled by CIA-A port B (PB0–PB7); support both output (to printer) and input modes
- /ACK — acknowledge input (active low) from the peripheral; triggers a level-2 interrupt on the Amiga, signalling that the previous byte was accepted and the interface is ready for the next
- BUSY — general-purpose bidirectional I/O line; when used with a printer, indicates the printer buffer is full
- POUT — paper-out status from the printer (bidirectional I/O)
- SEL — device-select line (bidirectional I/O); shared with the RS-232 ring-indicator signal
- GND — signal ground (pins 14–22)
- +5V — +5 V DC supply output (pin 23, 10 mA maximum); unique to the A1000
- n/c — pin 24 is not connected
- /RESET — system reset output (pin 25); present on the A1000 only