OSWORD &FE

OSWORD &FE (254) Z80 Tube FM disk access

Single density disk access (Z80 Tube OS)

This OSWORD call is installed by the Z80 v2 Tube client.

 On entry:
   XY?0   = &10 (send block length)
   XY?1   = &03 (receive block length)
          The rest of the block is a SCSI command block similar to OSWORD &72
   XY?2   = returned result, 0=ok, &00+n=HDD error, &40+n=FDD error
   XY!3   = data address
   XY?7   = command
   XY?8   = drive number in b5-b7, sector b16-b20 in b0-b4
   XY?9   = sector number b8-b15
   XY?10  = sector number b0-b7
   XY?11  = number of sectors (what does &00 mean?)
   XY?12  = drive flags, b7=drive 0, b6=drive 1, etc.
   XY?13  = drive 0 settings
   XY?14  = drive 1 settings
   XY?15  = etc.
   XY?20  = drive 7 settings

This is loaded by the Z80 Tube v2 client code from $.CPM.X (for BBC B/B+) or $.CPM.Y (for Master) from ADFS. It provides FM (single-density) disk access when DFS OSWORD &7F is not available. MFM (double-density) disk access is provided by OSWORD &72 on the assumption that if ADFS is present, which is implied by being able to load $.CPM.X from ADFS, then ADFS's OSWORD &72 is available.

The floppy disk layout used is 2 sides x 80 tracks x 10 sectors x 256 bytes FM.

Commands

 &08 Read data
 &09 Read Verify
 &0A Write data
 &0B Seek track

If the drive flag is set in XY?12, the drive setting in XY+13 onwards is used, and the drive seeks for track 0 before the operation.

Known code only implements command &08, &0A and &0B.

Results

 &00 Ok                                         &40 FDD Write protected
 &08 CRC error in data (FDC status &08)
 &10 Sector not found (FDC status &10)
 &18 CRC error in ID (FDC status &18)
 &20 Invalid command to controller              &60 Bad SCSI command
 &21 Illegal disc address - beyond end of disk  &61 Bad disc address
 &22 unused                                     &62 unused
 &23 Volume error                               &63 Volume error
 &24 Invalid parameter to controller            &64 Bad arguments
 &25 Illegal drive number                       &65 Bad drive
 &26 Invalid field in parameter list/Timeout    &66 Drive timed out
 &27 Unsupported controller command             &67 Unsupported SCSI command
 &2F Abort                                      &6F Abort

Bit 6 of the result is used to indicate if the error is from the hard drive controller or the floppy controller. Floppy errors are the same as hard drive errors, ORed with &40. Floppy errors are also the 1770 status byte ORed with &40.

However, the known OSWORD &FE driver omits setting &40 when returning the result.

Notes

• The default code fails if called from the I/O processor with the control block at &xxFE or &xxFF due to incrementing X without carrying the overflow into Y.

DOS Hard disk control (80x86 DOS)

The 6502 host support code in 6502.SYS installed by the 80x86 DOS just returns from OSWORD &FE.

See also

• OSWORD &72
• OSWORD &FE source code
• OSWORDs list at mdfs.net

Tube OSWORD calls
OSWORD &FA : Data transfer across Tube OSWORD &FB : MFM floppy disk access OSWORD &FC : DOS CRTC control OSWORD &FD : DOS Text control	OSWORD &FE : DOS Hard disk access OSWORD &FE : Z80 FM floppy disk access OSWORD &FF : DOS Fast screen access OSWORD &FF : Data transfer across Tube

Jgharston 14:29, 26 May 2009 (UTC) Jgharston 03:29, 20 July 2020 (CEST) Jgharston (talk)