Changes

Before accessing a disk you should first "Recalibrate" issue a ''recalibrate'' command to the drive, that moves to move the head backwards until it reaches Track 0. (The Track 0 the ''track zero'' signal from the drive is sensed by the FDC and it initializes . The FDC will also set its internal track counter for that drive to 0)zero.

On a an 80 -track drive you may need to repeat that twice because some models of the FDC stop after 77 steps and so if your recalibrating from track 80 it will 78 or above the controller might not recalibrate fullyreach track zero.

Now if you want In order to format, read or write a sector on a specific track you must first Seek ''seek'' that track (using command 0Fh). That'll move the read/write head to the physical track number. If you don't do that, then the FDC will attempt to read/write data to/from /to the current physical track, independenly irrespective of the specified logical Track-''track ID''.

The Track-''track'', Sector-''sector'', and Head-''head'' IDs are logical IDs only. These logical IDs are defined when formatting the disk, and aren't required to be identical to reflect the physical Tracktrack, Sectorsector, or Head head numbers. However, when reading or writing a sector you must specify the same IDs that have been used during formatting.

Despite the confusing name, a sector with a "''Deleted Data data Address Mark" '' (DAM) is not deleted. The ; the DAM-flag is just another ID-bit, . 'Deleted' sectors can be read/written just like normal data sectors and (if that ID-bit is specified correctly in the command) it can be read/written like normal data sectors.

At the end of a successful read/or write command, the program should send a ''Terminal Count '' (TC) signal to the FDC. However, in the CPC the TC pin isn't connected to the I/O bus, making it impossible for the program to confirm a correct operation. For that reason, the FDC will assume that the command has failed, and it'll return both Bit 6 in Status Register 0 and Bit 7 in Status Register 1 set. The program should ignore this error message.

The CPC doesn't support floppy DMA transfers, and the FDCs Interrupt signal isn't used in the CPC also.

Usually single sided 40 Track -track 3" disk drives are used in CPCs. For practical purposes, whereas 40 tracks is the official specification, practically 42 tracks could be used (— the limit is specific to the FDD, drive and some support more tracks. but 42 is a good maximum). The FDC controller can be used to control 80 -tracks, and/or double sided drives also, even though AMSDOS isndoesn't supporting support such formats. AMSDOS is supporting supports a maximum of two disk drives only.