Fujitsu MAW3073 SERIES Specifications page 71

4) If the INIT creates an attention condition then the TARG will go to a MESSAGE OUT phase,
receive all the message bytes, and cause an unexpected bus free by generating a BUS FREE
phase.
5) If the TARG detects the SEL signal being true, the TARG will release the BSY, MSG, C/D,
and I/O signals within one QAS release delay.
6) After waiting at least one QAS arbitration delay from negating the SCSI MSG, C/D, and I/O
signals in step 2), if there are no SCSI ID bits true the TARG will transition to the BUS FREE
phase.
7) After waiting at least one QAS arbitration delay from negating the MSG, C/D, and I/O signals
in step 2), if there are any SCSI ID bits true the TARG will wait at least a second QAS
arbitration delay. If the SEL signal is not true by the end of the second QAS arbitration delay
the TARG transitions to the BUS FREE phase.
Note :
The release of MSG, C/D, and I/O may cause release glitches; Step 5) above ensures these
glitches occur at a time when no connection is established on the bus so that they do not
interfere with proper operation.
The procedure for a SCSI device with QAS enabled to obtain control of the SCSI bus via QAS is
as follows:
1) The SCSI device shall first wait for MESSAGE IN phase to occur following a DT DATA
phase with a single QAS REQUEST message. When the SCSI device detects the ACK signal
being false for the QAS REQUEST message and the attention condition is cleared it shall
begin the QAS phase.
2) The SCSI device shall wait a minimum of two system deskew delays after detection of the
MSG, C/D, and I/O signals being false before driving any signal.
3) Following the delay in step 2), the SCSI device may arbitrate for the SCSI bus by asserting its
own SCSI ID within one QAS assertion delay from detection of the MSG, C/D, and I/O signals
being false. If arbitration fairness is enabled, the SCSI device shall not arbitrate until its
fairness register is cleared.
4) After waiting at least one QAS arbitration delay, measured from the detection of the MSG,
C/D, and I/O signals being negated, the SCSI device shall examine the DATA BUS.
A) If no higher priority SCSI ID bit is true on the DATA BUS and the fairness algorithm
allowed the SCSI device to participate, then the SCSI device has won the arbitration and
it shall assert the SEL signal.
B) If a higher priority SCSI ID bit is true on the DATA BUS or the fairness algorithm
prevented the SCSI device from participating in QAS arbitration, then the SCSI device
has lost the arbitration.
C) Any SCSI device other than the winner has lost the arbitration and shall release its SCSI
ID bit after two system deskew delays and within one QAS release delay after detection of
the SEL signal being true. A SCSI device that loses arbitration may return to step 1).
5) The SCSI device that wins arbitration shall wait at least one QAS arbitration delay after
asserting the SEL signal before changing any signals.
6) After the QAS arbitration delay in step 4), SCSI devices with arbitration fairness enabled that
are not arbitrating shall start sampling the DATA BUS to determine the SCSI devices that are
attempting arbitration, the SCSI device that won, and the SCSI devices that lost. This sampling
shall continue for one bus settle delay plus two system deskew delays. The SCSI devices shall
update their fairness register with all device IDs that lost arbitration.
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