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|

<columns>
===== 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

<newcolumn>
===== 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:
  * 62.5ns steps, must be set to 437.5ns
<newcolumn>
===== 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|
</columns>

===== 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 =====
  * Bit 7: set to 0 for inner tracks of disk. Compensate writes for the smaller disk surface.
  * Bit 6: ?

====== Sector format ======
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            |