Seagate Ultra 320 - Manual (Page 40)

26 Parallel SCSI Interface Product Manual, Rev. A )
2.5.1 Arbitration delay
The minimum time a SCSI device shall wait from asserting BSY for arbitration until the data bus can be exam-
ined to see if arbitration has been won (see Section 3.1.2). There is no maximum time.
2.5.2 ATN transmit setup time
When information unit transfers are not being used, the ATN transmit setup time is the minimum time provided
by the transmitter between the assertion of the ATN signal and the last negation of the ACK signal in any
phase.
When information unit transfers are being used with synchronous transfers, the ATN transmit setup time is the
minimum time provided by the transmitter between the assertion of the ATN signal and the negation of the ACK
signal corresponding to the last iuCRC transfer of an information unit.
When information unit transfers are being used with paced transfers, the ATN transmit setup time is the mini-
mum time provided by the transmitter between the assertion of the ATN signal and the assertion of the ACK
signal corresponding to the last iuCRC transfer of an information unit.
Specified to provide the increased ATN receive setup time, subject to intersymbol interference, cable skew,
and other distortions.
2.5.3 ATN receive setup time
When information unit transfers are not being used, the ATN receive setup time is the minimum time required
at the receiver between the assertion of the ATN signal and the last negation of the ACK signal in any phase to
recognize the assertion of an attention condition.
Table 10: SCSI fast-160 and fast-320 interconnect timing budget in nanoseconds
Item Fast-160 Fast-320 Comments
Nominals:
REQ(ACK) period 12.5 6.25 from table 6
Transfer period 6.25 3.125 REQ(ACK) period/2
Transmitter and receiver errors:
Total
Errors
Post
Compens
ation
Total
Errors
Post
Compens
ation
Worst case total of + and -
time shift except where noted
Interconnect errors:
Cable skew
a b 2.5 0 2.5 0
Crosstalk time shift 0.7 0.7 0.5 0.5 Time impact
ISI of data 4.0 2.0 4.0 1.0 Worse case pattern
Total interconnect budget 7.2 2.7 7.0 1.5
a See 2.5.8.
b The residual deskew error is included in the receiver error budget.
Note. For more information on interconnect errors see the SCSI Passive Interconnect Performance standard.