atzsc —
A2091 low level SCSI interface
The Amiga architecture uses a common machine independent scsi sub-system
  provided in the kernel source. The machine independent drivers that use this
  code access the hardware through a common interface. (see
  scsibus(4)) This common
  interface interacts with a machine dependent interface, such as
  atzsc, which then handles the hardware specific
  issues.
The atzsc interface handles things such as
    DMA and interrupts as well as actually sending commands, negotiating
    synchronous or asynchronous transfers and handling disconnect/reconnect of
    SCSI targets. The hardware that atzsc uses is based
    on the WD33c93 SCSI chip.
The atzsc interface supports the following Zorro II
  expansion cards:
  - A2091
- Commodore SCSI adapter, manufacturer 514, product 2 or
      product 3
 
  - sbicwait TIMEO @%d with asr=x%x csr=x%x
- The 33c93 code (sbic) has been waiting too long for a SCSI chip operation
      to complete. %d is the line in the source file
      amiga/dev/sbic.c at which the SCSI chip timed-out.
      Asr and csr are status registers within the SCSI chip.
- atzsc%d: abort %s: csr = 0x%02x, asr = 0x%02x
- A SCSI operation %s was aborted due to an error.
- atzsc%d: csr == 0x%02i
- A error has occurred within the SCSI chip code.
- atzsc%d: unexpected phase %d in icmd from %d
- The target described by ‘from %d’ has taken the SCSI bus
      into a phase which is not expected during polled IO.
- atzsc%d: unexpected phase %d in icmd from %d
- The target described by ‘from %d’ has taken the SCSI bus
      into a phase which is not expected during DMA IO setup.
Theatzsc interface first appeared in
  NetBSD 1.0