Quantum 10K II - Manual (Page 322)

Quantum Atlas 10K II Ultra 160/m SCSI Hard Disk Drives B–1
Appendix B
SCSI REFERENCE INFORMATION
Appendix B provides information about SCSI bus timing, SCSI signal states, SCSI bus
conditions, and SCSI message format and supported SCSI messages. Information in this
appendix covers both SCSI-2 and SCSI-3 interfaces. Note that this information is general in
nature, and is not specific to the ATLAS 10K II disk drive. It is provided as a reference only.
B.1 SCSI-2 Bus Timing
Table B–1 provides timing values and definitions for SCSI-2 SCSI bus signals.
Table B–1 SCSI Bus Timing Values -- ANSI SCSI-2 Standard
Timing Description Value Description
Arbitration Delay 2.4 µs Minimum time a SCSI device waits from asserting
BSY for arbitration until the DATA BUS can be
examined to see if arbitration has been won; there
is no maximum time.
Assertion Period 90 ns Minimum time a drive asserts REQ while using
standard synchronous data transfers; also, the
minimum time that an initiator asserts ACK while
using standard (slow) synchronous data transfers.
Bus Clear Delay 800 ns Maximum time for a SCSI device to stop driving
all bus signals after:
1. BUS FREE is detected.
2. SEL is received from another SCSI device
during ARBITRATION.
3. Transition of RST to true.
For condition 1, the maximum time for a SCSI
device to clear the bus is 1200 ns (1.2 µ s) from
BSY and SEL first becoming both false.
If a SCSI device requires more than a bus settle
delay to detect BUS FREE, it clears the bus within a
bus clear delay minus the excess time.
Bus Free Delay 800 ns Maximum time a SCSI device waits from its
detection of BUS FREE until its assertion of BSY
when going to ARBITRATION.
Bus Set Delay 1.8 µs Maximum time for a device to assert BSY and its
SCSI ID bit on the DATA BUS after it detects BUS
FREE to enter ARBITRATION.
Bus Settle Delay 400 ns Minimum time to wait for the bus to settle after
changing certain control signals as defined in
protocol definitions.