Appendix B. SCSI Bus Signal Timing
B–6 Quantum Atlas 10K II Ultra 160/m SCSI Hard Disk Drives
Table B–4 Double Transition (DT) SCSI Bus Data and Information Phase Timing
Values (Note 4)
Timing Description Fast-10 Fast-20 Fast-40 Fast-80
ATN Transmit Setup Time 48.4 ns 29.2 ns 19.6 ns 14.8 ns
ATN Receive Setup Time 13.6 ns 7.8 ns 4.9 ns 3.45 ns
Cable Skew (note 1) 4 ns 3 ns 2.5 ns 2.5 ns
pCRC Receive Hold Time 10.2 ns 5.1 ns 2.55 ns 1.45 ns
pCRC Receive Setup Time 20.2 ns 15.1 ns 12.55 ns 11.45 ns
pCRC Transmit Hold Time 37 ns 18.5 ns 9.25 ns 4.8 ns
pCRC Transmit Setup Time 47 ns 28.5 ns 19.25 ns 14.8 ns
Receive Assertion Period (note 2) 80 ns 40 ns 20 ns 10 ns
Receive Hold Time (note 2 and note 3) 11.6 ns 5.8 ns 2.9 ns 1.45 ns
Receive Negation Period (note 2) 80 ns 40 ns 20 ns 10 ns
Receive Setup Time (note 2 and note 3) 11.6 ns 5.8 ns 2.9 ns 1.45 ns
Receive REQ (ACK) Period Tolerance 0.7 ns 0.7 ns 0.7 ns 0.7 ns
Signal Timing Skew 26.8 ns 13.4 ns 6.7 ns 3.35 ns
REQ (ACK) Period 200 ns 100 ns 50 ns 25 ns
Transmit Assertion Period (note 2) 92 ns 46 ns 23 ns 11.5 ns
Transmit Hold Time (note 2 and note 3) 38.4 ns 19.2 ns 9.6 ns 4.8 ns
Transmit Negation Period (note 2) 92 ns 46 ns 23 ns 11.5 ns
Transmit Setup Time (note 2 and note 3) 38.4 ns 19.2 ns 9.6 ns 4.8 ns
Transmit REQ (ACK) Period Tolerance 0.6 ns 0.6 ns 0.6 ns 0.6 ns
Notes: 1 Cable Skew is measured at each device connection with the transmitted skew subtracted from
the received skew.
2 See SPI-3 specifications for measurement points.
3 See SPI-3 specifications for examples of how to calculate setup and hold timing.
4 SCSI bus timing values specified by the maximum transfer rate for the given range shall apply
even if a slower transfer rate within the given range is negotiated.
