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7.4 Timing Rule
Table 7.6 gives the timing required for operations on the SCSI bus.
When [Transfer Period] is less than 200 ns in synchronous data transfer mode, Asserion Period,
Cable Skew Delay, Deskew Delay, Hold Time, Negation Period is changed FAST SCSI and
used in FAST SCSI timing required fpr operation. (Table 7.7)
Table 7.6 Timing specifications (1 of 3)
No. Name Standard Timing specification
1 Arbitration Delay 2.4 µs min. The minimum wait period between the time the
SCSI device sends a BSY signal and the time the
value on the data bus for determining the priority of
bus use is judged in the ARBITRATION phase. A
maximum time is not defined.
2 Assertion Period 90 ns min. Minimum pulse width of an ACK signal sent by
INIT and an REQ signal sent by TARG for
synchronous data transfer.
3 Bus Clear Delay 800 ns max. Maximum allowable period between the time either
of the following events occurs and the time the SCSI
device stops driving all bus signals.
(1) Detection of the BUS FREE phase (when both
BSY and SEL signal become false during Bus
Settle Delay).
Note:
Maximum allowable period between the
time both BSY and SEL signal became
false and the time the bus is released is
1,200 ns.
An SCSI device that requires a period
longer than Bus Settle Delay for the
detection of the BUS FREE phase must
release the bus within (Bus Clear Delay)
minus (Bus Settle Delay excess time).
(2) Another SCSI device asserts the SEL signal
during an ARBITRATION phase.
(3) The RST signal becomes true (RESET
condition).
4 Bus Free Delay 800 ns min. Minimum wait period between the time the SCSI
device detects a BUS FREE phase and the time it
sends a BSY signal to initiate an ARBITRATION
phase.
5 Bus Set Delay 1.8 µs max. Maximum allowable period between the time an
SCSI device detects a BUS FREE phase and the
time it sends BSY and SCSI ID signals to initiate an
ARBITRATION phase.
Table 7.6 Timing specifications (2 of 3)