NAME
       ADCMD_FINISH -- abort writes in progress to audio channels

   FUNCTION
       ADCMD_FINISH is a command for multiple audio channels.  For each
       selected channel (io_Unit), if the allocation key (ioa_AllocKey) is
       correct and there is a write (CMD_WRITE)in progress, ADCMD_FINISH
       aborts the current write immediately or at the end of the current
       cycle depending on the sync flag (ADIOF_SYNCCYCLE).  If the allocation
       key is incorrect ADCMD_FINISH returns an error (ADIOERR_NOALLOCATION).
       ADCMD_FINISH is synchronous and only replies (mn_ReplyPort) if the
       quick flag (IOF_QUICK) is clear.  Do not use ADCMD_FINISH in interrupt
       code at interrupt level 5 or higher.

   INPUTS
       mn_ReplyPort- pointer to message port that receives I/O request
                     if the quick flag (IOF_QUICK) is clear
       io_Device   - pointer to device node, must be set by (or copied from
                     I/O block set by) opendevice function
       io_Unit     - bit map of channels to finish (bits 0 thru 3 correspond
                     to channels 0 thru 3)
       io_Command  - command number for ADCMD_FINISH
       io_Flags    - flags, must be cleared if not used:
                     IOF_QUICK      - (CLEAR) reply I/O request
                     ADIOF_SYNCCYCLE- (CLEAR) finish immediately
                                      (SET) finish at the end of current
                                            cycle

       ioa_AllocKey- allocation key, must be set by (or copied from I/O block
                     set by) opendevice function or adcmd_allocate command

   OUTPUTS
       io_Unit     - bit map of channels successfully finished (bits 0 thru 3
                     correspond to channels 0 thru 3)
       io_Error    - error number:
                     0                    - no error
                     ADIOERR_NOALLOCATION - allocation key (ioa_AllocKey)
                                            does not match key for channel