OSWORD &72

OSWORD &72 (114) - Perform SCSI/MFM disk operation

Specification

   On entry:
       XY?0  = 0, returned result
       XY!1  = data address
       XY?5  = command
       XY?6  = drive number in b5-b7, sector b16-b20 in b0-b4
       XY?7  = sector number b8-b15
       XY?8  = sector number b0-b7
       XY?9  = number of sectors or 0
       XY?10 = 0
       XY!11 = data length if X%?9=0

This is a standard SCSI command block. The drive number in XY?6 is ORed with the current drive. If ADFS is not selected when the call is made, ADFS is selected. Consequently, any code that calls OSWORD &72 must remember the current filing system and restore it afterwards.

Commands

   &00=Test drive ready
   &01=Seek track 0
   &03=Request status
   &08=Read data
   &0A=Write data
   &0B=Seek track
   &1B=Stop/Start drive; stop if XY?9=0, start if XY?9=1

Results

   &00=Ok
   &02=Drive door open
   &03=Media error, eg disk dirty
   &05=Bad SCSI command
   &04=Not ready
   &40=Write protected
   &48=CRC error
   &50=Sector not found
   &60=Bad command
   &61=Bad address
   &63=Volume error
   &65=Bad drive
   &6F=Abort

The result byte can be preloaded with a value to return if no OSWORD &72 routine exists. For instance, preloading the result with &00 makes all such failed calls appear to succeed, preloading with &50 makes all calls appear to return 'Sector not found'.

Coding

The following routine can be used to perform an OSWORD &72 call. It requires X%=>15-byte control block, Y%=X%DIV256.

   DEFFNscsi(cmd%,addr%,num%,sect%,drv%):LOCALfs%
   fs%=FNfs:IFfs%<>8:*FX143,18,8
   X%?0=0:X%!1=addr%:X%?5=cmd%:X%?6=drv%*32+((sect%AND&1F0000)DIV65536)
   X%?7=((sect%AND&FF00)DIV256):X%?8=sect%:X%!9=0:X%!11=num%
   A%=&72:CALL&FFF1:A%=?X%:IFfs%<>8:OSCLI"FX143,18,"+STR$ fs%
   =A%
   DEFFNfs:LOCALA%,E%,Y%:=(USR&FFDA)AND&FF

Cumana Electron DFS disk access

The Cumana Double Densisty Electron DFS implments the following OSWORD &72 call:

   On entry:
       XY?0  = Control byte,
               b0: side select 0,1
               b1: drive 1 select
               b2: drive 2 select
               b3: 0=double density, 1=single density
       XY?1  = command
       XY?2  = track
       XY?3  = sector
       XY?4  = data
       XY!5  = address
       XY?9  = 0, holds result on exit

Commands

   &04=Seek track zero
   &14=Seek track
   &50=Step in one track
   &70=Step out one track
   &80=Read sector
   &A0=Write sector
       b0-b1=step rate 6ms/12ms/20ms/30ms

Results

   XY?2=new track
   XY?3=new sector
   XY?9=result
        &00=Ok

See Also

• http://mdfs.net/Docs/Comp/BBC/Osword/Osword72
• http://mdfs.net/Docs/Comp/BBC/Oswords

Jgharston 14:06, 26 May 2009 (UTC)