Quantum DLT 4000 Manual descargar pdf (Pagina 70)

SCSI Description

3-8 Quantum DLT 4000 Tape Drive

Table 3–4 SCSI Bus Timing Values

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

synchronous data transfers; also, the minimum time

that an initiator asserts ACK while using 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 µs) 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 called out in the

protocol definitions.

Cable Skew Delay 10 ns Maximum difference in propagation time allowed

between any two SCSI bus signals measured between

any two SCSI devices.

Recommended Time.

1 2 ... 65 66 67 68 69 70 71 72 73 74 75 ... 299 300

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Quantum DLT 4000 Manual Pagina 70