PC-9801 External Floppy Drive connector pinout
These connectors are present on NEC PC-9801.
Two 3.5/5.25/8-inch 1.2MB drives can be connected to External floppy disk drive connector.
Two 3.5/5.25-inch 640/720KB/1.2MB drives can be connected to Internal floppy disk drive connector.
Bibliography:
- HAMLIN's PAGE
- NEC Corporation (1986): PC-9801VX Hardware Manual.
External floppy disk drive connector (50-pin micro ribbon)
25 - 1
50 - 26
Internal floppy disk drive connector (34-pin IDC)
2, 4, 6,..., 34
1, 3, 5,..., 33
| Pin(ex) | Pin(in) | Description | Dir | Pull up |
| 1 | 3 | Window |  |
O |
| 2 | 7 | MFM/FM Select |  |
O |
| 3 | 30 | Read Data | |
O |
| 4 | 28 | Write Protect | |
O |
| 5 | 26 | Track 00 | |
O |
| 6 | 24 | Write Gate | |
O |
| 7 | 22 | Write Data | |
O |
| 8 | 20 | Step Pulse | |
O |
| 9 | 18 | Direction | |
O |
| 10 | 6 | Drive Select 3 | |
O |
| 11 | 14 | Drive Select 2 | |
O |
| 12 | (6) | (Drive Select 1)(*) | |
O |
| 13 | (14) | (Drive Select 0)(*) | |
O |
| 14 | 11 | Sync | |
O |
| 15 | 34 | Ready | |
O |
| 16 | 8 | Index | |
O |
| 17 | 4 | Head Load | |
O |
| 18 | x | n/c | - | - |
| 19 | 32 | Side Select | |
O |
| 20 | x | n/c | - | - |
| 21 | x | Two Sided | |
O |
| 22 | x | n/c | - | - |
| 23 | x | File Unsafe | |
O |
| 24 | x | File Unsafe Reset | |
? |
| 25 | x | Low Write Current | |
? |
| x | 2 | Density Select | |
O |
| x | 10 | Drive Select 0 | |
O |
| x | 12 | Drive Select 1 | |
O |
| x | 16 | Motor On | |
O |
| x | 17 | n/c(Drive Selected) | |
- |
| x | 33 | GND(Disk Change) | |
- |
| 26-50 | 1,5,9 ,13,15 ,19,21 ,23,25 ,27,29 ,31 |
Ground | - | - |
Note: Dir is Disk controller relative Disk drive.
Note: On early models, (ex)pin 12 is used as "Drive Select 1" and (ex)pin 13 is used as "Drive Select 0". On later models installed two internal disk drives, (ex)pin 10 and (ex)pin 12 are the same as (ex)pin 11 and (ex)pin 13. Because of this, later models cannot use more than 3 external floppy drives.
