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Table 4.4Signal delay times definition (3/3)
No. Item Time Definition
14 Reset to
selection
time
250 ms
(recom-
mended)
The recommended maximum time after a hard RESET
condition until an SCSI target is able to respond with
appropriate status and sense data to the TEST UNIT
READY, INQUIRY, and REQUEST SENSE commands
15 Reset hold
time
25 µs The minimum time over which RST must be kept asserted
16 Selection
abort time
200 µs The maximum time required from the moment when
selection or deselection of an initiator or target is detected
until BSY is asserted
17 Selection
timeout
delay
250 ms
(recom-
mended)
The minimum time required for an initiator or target in
the selection or deselection phase to wait for a BSY
response before it starts the timeout procedure
18 Transfer
period
The minimum allowable period, during sync data
transfer, between the start of consecutive REQ pulses and
the start of consecutive ACK pulses
4.3.1 BUS FREE phase
The BUS FREE phase is used to indicate that no SCSI device is actively using the
SCSI bus, and that it is available.
SCSI devices shall detect the BUS FREE phase after the SEL and BSY signals are
both false for at least a bus settle delay.
SCSI devices shall release all SCSI bus signals within a bus clear delay after the
BSY and SEL signals become continuously false for a bus settle delay.
bus clear delaybus settle delay
BSY
SEL
others
BUS FREE phase
4 − 12