Changes
Created page with " == MFM == Some FDCs are quite relaxed in the data that they accept. The following applies to the NEC D765AC-2 and was found through testing: * The only address mark which i..."
== MFM ==
Some FDCs are quite relaxed in the data that they accept. The following applies to the NEC D765AC-2 and was found through testing:
* The only address mark which identifies the ID field is 0x0fe. Attempting to use any other mark for an ID field will result in the ID field being ignored.
* The only data marks which identify the data field are 0x0fb (Data) and 0x0f8 (Deleted Data). Attempting to use any other mark fo a data field will result in the field being ignored.
* Only 3 sync marks (4489) can proceed an ID field or data field. Fewer or more are ignored.
* When a valid ID field has been read, the data field must be found within a certain number of bytes from the end of the ID field. The minimum is 33 bytes. The maximum is around 44 but needs to be determined.
* Sector within sector is possible.
* If an ID field with a CRC error is found then the data field will not be read when using Read Data or similar commands.
* Any data can exist in Gap 2 and will not affect reading of the ID fields or sectors.
* Any data can exist in Gap 3 and will not affect reading of the ID fields or sectors.
