***************************************************************
*                                                             *
*      Module Name: RESTORE.LIB          Rev. 1.00            *
*      Function: Return drive head       Last rev. 06 May 85  *
*                to track 0              By: glh/w6bsk        *
*                                                             *
***************************************************************

*    Equ table

cmdreg    equ  0fce3h         ; Morrow DJ 1791 command port
restor    equ  0009h          ; 1791 Type 1 restore command
trak0     equ  0004h          ; 1791 Track 0 mask


restore:
          lxi  h,cmdreg       ; Point to 1791 command register
          mvi  m,restor       ; and enter the go-to-track-0
unbusy:                       ; command.
          mov  m,a            ; Load the status byte and test for
          rar                 ; busy. Keep checking until busy
          jnc  unbusy         ; flag is raised.
busy:
          mov  a,m            ; Then loop until the busy flag
          rar                 ; goes down.
          jc   busy
          mov  a,m            ; Load the status byte and test for
          ani  trak0          ; at-track-0 flag. If flag is not
          jz   reserr         ; raised, do error jump.
          ret                 ; Else done, go home.
reserr:
          call ccrlf
          call spmsg          ; Display error
          db   ' * Track 0 error: drive failure *',0
          ret                 ; with z flag set.