Interface info   6/21/92

Slave R1 command word:
  Bit	Hex
   31   80000000 - Interface reset
   15   00008000 - Halt interface
   14   00004000 - Clear exception status
                   (Enable exceptions caused by timeout)
   13   00002000 - Resume after error acknowledgement
                   (Enable exceptions caused by cam interrupt)
   12   00001000 - Enable new list (host next pointer driven)
                   interrupt
   11   00000800 - Enable timeout interrupt
   10   00000400 - Enable Sbus interrupt
    9   00000200 - Enable CAM interrupt
    8   00000100 - Enable soft interrupt
    6   00000040 - Disable exceptions caused by timeout
    5   00000020 - Disable exceptions caused by cam interrupt
    4   00000010 - Disable new list interrupt
    3   00000008 - Disable timeout interrupt
    2   00000004 - Disable Sbus interrupt
    1   00000002 - Disable CAM interrupt
    0   00000001 - Disable soft interrupt

Slave R1 status word:
  Bit	Hex
   14   00004000 - Exceptions caused by timeout enabled
   13   00002000 - Exceptions caused by cam interrupt enabled
   12   00001000 - New list interrupt enable
   11   00000800 - Timeout interrupt enable
   10   00000400 - Sbus interrupt enable
    9   00000200 - CAM interrupt enable
    8   00000100 - Soft interrupt enable
    4   00000010 - New list interrupt
    3   00000008 - Timeout interrupt
    2   00000004 - Sbus interrupt
    1   00000002 - CAM interrupt
    0   00000001 - Soft interrupt

Slave R0 status word:
 31-4   nnnnnnnX - Host next pointer
    3   00000008 - Interface halted (OR of deliberate halt and exception status)
    2   00000004 - Waiting for host
    1   00000002 - Exception status (CAM timeout, or CAM interrupt)
    0   00000001 - Host next pointer written

Slave R2 status word:
 31-4   nnnnnnnX - Step list pointer
    3   00000008 - Waiting to transfer (set by cam wait flag;
                     cleared when done counter is loaded)
    2   00000004 - Done status (from CAM word counter)
    1   00000002 - Partial write to cam after Sbus error
    0   00000001 - Sbus fsm suspended because of Sbus error


Slave R3 status word:
 31-4   nnnnnnnX - Previous step list pointer
    3   00000008 - Interface reset pending
    2   00000004 - Reserved for Sparc 2 bit
    1   00000002 - CAM scanning status (1=scanning) (decode of eosi signal)
    0   00000001 - CAM interrupt status (decode of eosi signal)




R0 Control Register bit definitions:

  Bit	Hex
  31	80000000 - reset CAM (must be part of NOOP)
  30	40000000 - CAM read 
  29	20000000 - Immediate data
  28	10000000 - Flg8
  15	00008000 - Host jump; use the host next pointer if it
				has been written
  14	00004000 - Host wait
  13	00002000 - Soft interrupt
  12	00001000 - wait for CAM EOS before executing instruction
  5-0	0000003f - opcode (register select)

2/12/91
  An exception prevents setting the hnp written flag.

  The CAM reset signal is accomplished by turning on the
    reset CAM, CAM read, and Immediate data bits of the
    control word; the count from R2 determines the length
    of the reset pulse.

  The interface reset pulse is one Sbus clock wide,
    triggered on falling edge of clock.

  An Sbus error causes the Sbus fsm to into a suspended
    state, setting the "suspended" status bit.  This
    bit is cleared by writing to bit 13 of the Slave R1
    command word.  The "partial write" bit indicates
    whether any of the erroneous data was sent to cam.

  An Sbus error no longer sets the exception status.

4/25/91
  A cam interrupt will not set exception status or stop
the sbus state machines *until* the cam interrupt is enabled
at least once after an interface reset.