| signal | function | Unidisk | IIc | IIgs | Disk ][ |
|---|---|---|---|---|---|
| GND | ground | 1-4 | 1-4 | 1-3 | 1,3,5,7 |
| -12V | -12 volts DC | 5 | 5 | 5 | 9 |
| +5V | +5 volts DC | 6,16 | 6 | 6 | 11,12 |
| +12V | +12 volts DC | 7,8 | 7,8 | 7,8 | 13,15,17,19 |
| WRPROT | write protect | 10 | 10 | 10 | 20 |
| PH 0-3 | stepper motor phases | 11-14 | 11-14 | 11-14 | 2,4,6,8 |
| WRREQ | write request | 15 | 15 | 15 | 10 |
| ENBL | drive enable (low) | 17, (9) | 17 | 17,(9) | 14 |
| RDDATA | read data | 18 | 18 | 18 | 16 |
| WRDATA | write data | 19 | 19 | 19 | 18 |
| EXTINT | external interrupt | - | 9 | - | |
| not connected | - | 16 | - | ||
| 3.5DISK | Apple 3.5 drive enable | - | - | 4 | - |
| HDSEL | 3.5" drive head select | - | - | 16 | - |
To use Unidisk with Apple IIgs, connect pin 4 to GND and pin 16 to +5V
- REF1: https://archive.org/details/Open_Apple-Vol_1_No_11-DEC_1985/page/n1
- REF2: http://wiki.apple2.org/index.php?title=Pinouts
+-------------------------------------------------+
| 2 4 6 8 10 12 14 16 18 20 |
| 1 3 5 7 9 11 13 15 17 19 |
+-------------------------------------------------+
IDC20 pin (The above numbering is from the back of the plug (where the ribbon cable connects to the plug)
DB19
,-------------------------------------------------.
\ 1 2 3 4 5 6 7 B 9 10 /
\ 11 12 13 14 15 16 17 18 19 /
`---------------------------------------------'