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Table 4.4 Signal delay times definition (2/3)
No. Item Time Definition
4 Bus free delay 800 ns The minimum time that an SCSI device shall wait from
its detection of the BUS FREE phase (BSY and SEL both
false for a bus settle delay) until its assertion of BSY
when going to the ARBITRATION phase
5 Bus set delay 1.8 os The maximum time for an SCSI device to assert BSY and
its SCSI ID bit on the DATA BUS after it detects BUS
FREE phase (BSY and SEL both false for a bus settle
delay) for the purpose of entering the ARBITRATION
phase
6 Bus settle
delay
400 ns The minimum time to wait for the bus to settle after
changing certain control signals as called out in the
protocol definitions
7 Cable skew
delay
10 ns The maximum difference in propagation time allowed
between any two SCSI bus signals measured between
any two SCSI devices
8 Data release
delay
400 ns The maximum time for an initiator to release the DATA
BUS signals following the transition of the I/O signal
from false to true
9 Deskew delay 45 ns The minimum time required for deskew of certain
signals
10 Disconnection
delay
200 os The minimum time that a target shall wait after
releasing BSY before participating in an ARBITRATION
phase when honoring a DISCONNECT message from the
initiator
11 Hold time 45 ns The minimum time added between the assertion of REQ
(or REQB) or ACK (or ACKB) and the changing of the
data lines to provide hold time in the initiator or target
while using synchronous data transfers. REQB and
ACKB timings only apply to optional wide data
transfers.
12 Negation
period
90 ns The minimum time that a target shall negate REQ (or
REQB) while using synchronous data transfers. Also,
the minimum time that an initiator shall negate ACK (or
ACKB) while using synchronous data transfers. REQB
and ACKB timings only apply to optional wide data
transfers.
13 Power>on to
selection time
10 sec
(recom>
mended)
The recommended maximum time from power
application until an SCSI target is able to respond with
appropriate status and sense data to the TEST UNIT
READY, INQUIRY, and REQUEST SENSE commands
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