The THMFC1 is a custom floppy controller developed by Thomson and used in the TO8, TO9+, and TO8D, as well as the floppy controller expansion for the MO6 (which also works on older machines). It's a very flexible floppy controller, as it leaves a big part of the work to the CPU. One interesting fact is the ability to use QDD drives as well as regular floppies.
Register map
| Address | Name | Description |
| E7D0 | STAT0/CMD0 | status/command |
| E7D1 | STAT1/CMD1 | status/command |
| E7D2 | CMD2 | command |
| E7D3 | WDATA/RDATA | data read/write |
| E7D4 | WCLK | clock (MFM bits) |
| E7D5 | WSECT | sector |
| E7D6 | WTRCK | track |
| E7D7 | WCELL | cell size adjust |
E7D0: CMD0
| Bit | Description |
| 7 | Must be 0 |
| 6 | Must be 0 |
| 5 | MFM (0)/ FM (1) |
| 4 | Enable sync detection |
| 3 | Disable sync detection (format track) |
| 2 | Write enable |
| 1,0 | Operation code |
Operations:
00: reset
01: write sector
10: read address
11: read sector
|
E7D1: CMD1
| Bit | Description |
| 7 | Compatibility |
| 6,5 | Sector length |
| 4 | Side select |
| 3-1 | Timing compensation |
| 0 | Enable READY signal detection |
Sector sizes:
00: 128 bytes
01: 256 bytes
10: 512 bytes
11: 1024 bytes
Timing compensation:
|
E7D2: CMD2
| Bit | Description |
| 6 | Side select |
| 5 | Step direction (0 = towards track 0) |
| 4 | Step |
| 2 | Motor on |
| 1 | Drive select 1 |
| 0 | Drive select 0 |
|
E7D0: STAT0
| Bit | Description |
| 7 | Character clock image (?) |
| 6,5 | Must be 0 |
| 4 | Operation finishing |
| 3 | Operation finished |
| 2 | CRC error |
| 1 | Similar to bit 7, for automated operations |
| 0 | Sync detection |
E7D1: STAT1
| Bit | Description |
| 7 | Must be 0 |
| 6 | Index pulse detection |
| 5 | Disk change |
| 4 | Motor state (1=stopped) |
| 3 | Track 0 |
| 2 | Write protected |
| 1 | Ready |
E7D4: clock type
Must be set to FF when writing data bytes, or 0A when writing synchronization bytes (inter-sector gaps). Other values may be used for custom disk formatting, at your own risk.
E7D7: WCELL
The controller uses the standard shugart MFM coding for sectors, but can be programmed to do other things as well.
| | Byte count | Contents | Description |
| Header | 12 | 00 | Bit synchronization |
| 3 | A1 clock 0A | Char synchronization |
| 1 | FE | Header mark |
| 1 | | Track id |
| 1 | | Side id |
| 1 | | Sector id |
| 1 | | Sector size |
| 2 | | CRC check |
| 22 | | Header GAP |
| Data | 12 | 00 | Bit synchronization |
| 3 | A1 clock 0A | Char synchronization |
| 1 | FE | Data mark |
| sector length | | Data |
| 2 | | CRC check |
| variable | | Data GAP |
