Quantum DLT1/VS80 SCSI, Interface Manual

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DLT1/VS80 SCSI Interface Guide
81-81276-01 Rev A01 July 2004 2-3
2.5 Behavior Around Power-On and SCSI BUS
RESET
In the following situations, the tape drive generates these responses:
The tape drive recognizes multiple bus resets in succession and bus resets of arbitrarily long duration.
It recovers within the time limits specified above following the last bus reset.
2.6 Data Cache and Medium Write Interaction
The tape drive contains a data cache that buffers blocks (records) until writing them. This section
defines specific times that the tape drive writes blocks to medium. A MODE SELECT parameter
allows disabling the data cache (unbuffered mode). In this mode, every WRITE command causes the
tape drive to write data to the data cartridge before returning the STATUS byte and the COMMAND
COMPLETE messages to the host.
N
OTE
: We do not recommend unbuffered mode because it produces poor
performance.
Table 2-1. Tape Drive Behavior after a Power-On and SCSI BUS RESET
Situation Tape Drive Response
Tape drive power off All tape drive SCSI lines go to high impedance.
Tape drive power on The tape drive does not generate any spurious signals on
the SCSI bus
Within 5 seconds of power on and within 250
milliseconds (typically under 4
ms) after a BUS
RESET
The tape drive responds to SCSI bus selections and
returns appropriate, normal responses. The tape drive
returns medium motion commands with CHECK
CONDITION status, Sense Key Not Ready, until the
media is ready.
The tape drive implements the Hard BUS RESET option.
The tape drive rewinds the medium to BOP (Beginning
of Partition, i.e. Beginning of Medium).