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Interface Rules for the SCSI Firmware
5-5
5
RTE required, or the RTE entry ($FFFE079A) RTE required as
status code $xx04 above. This intermediate status only
happens when the TARGET role is enabled.
All final status code returns use bits 15 through 13 of the status word in the
packet (second word of the user’s packet) to tell you about the condition of the
SCSI firmware and of the SCSI bus.
BIT 15: FINAL=(0)/INTERMEDIATE=(1) STATUS bit. For all final
status return codes, this bit is 0.
BIT 14: ADDITIONAL STATUS bit. For all final status returns, if this
bit is 1, additional status may be found in the additional status
area (CT +$74). If this bit is 0, no additional status is provided.
BIT 13: RTE bit. If this bit is a 0, an RTE is required to finish an
interrupt thread. When this bit is 0, A3 contains a pointer to a
register save area where D0 through D7 and A0 through A6
were saved. If the RTE is to be executed, the registers in the
register save area must first be restored. If this bit is a 1, no
RTE is to be executed.
The return mechanism on the final status codes only involve bits 13 of the user
status word (packet word 2). You MUST follow the priority scheme below if
you wish to interface to the SCSI firmware successfully.
RETURN CODE:
CAUTION
Care must be taken not to modify the contents of
register A3 when the RTE entry is taken.
Rule 3: ALL FINAL RETURNS MUST EXIT (THE
DRIVER)
PROPERLY THROUGH RTE, COME-
AGAIN, OR
REACTIVATION.