Quantum DLT 4000 Manual descargar pdf (Pagina 78)

SCSI Description

3-16 Quantum DLT 4000 Tape Drive

The initiator:

8. Determines that it is selected when the following occur for at least one bus

settle delay: SEL, I/O, and the initiator’s SCSI ID bit are true and BSY is

false.

9. Examines the DATA BUS to determine the SCSI ID of the reselecting drive.

10. Asserts the BSY signal within a selection abort time of its most recent

detection of being reselected.

The initiator does not respond to a RESELECTION phase if bad parity is

detected or if more than two SCSI ID bits are on the DATA BUS.

The drive:

11. Detects the BSY signal is true.

12. Asserts the BSY signal.

13. Waits at least two deskew delays.

14. Releases the SEL signal.

15. The drive can then change the I/O signal and the DATA BUS.

The initiator:

16. Detects the SEL signal is false.

17. Releases the BSY signal.

The drive:

18. Continues asserting the BSY signal until it relinquishes the SCSI bus.

3.5.4.2 Reselection Time-Out

Two optional time-out procedures are specified for clearing the SCSI bus if the

initiator waits a minimum of a selection time-out delay and there has been no

BSY signal response from the drive.

1. The initiator asserts the RST signal.

2. The initiator follows these steps:

a) Continues asserting the SEL and ATN signals and releases the DATA

BUS.

b) If it has not detected the BSY signal to be true after at least a selection

abort time plus two deskew delays, releases the SEL and ATN signals,

allowing the SCSI bus to go to the BUS FREE phase.

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Quantum DLT 4000 Manual Pagina 78