Viper 60s Theory Of Operation And Maintenance Manual page 119

VIPER SCSI COMMANDS
DC 600 A QIC - 24
300 XLP
- 24
5.21.5.3 Explicit Mode
The Viper drive enters the explicit mode either by
0),
reading a tape, (2) writing a tape, or (3)
with density code field set to non-zero in the MODE SENSE command.
If the Viper drive is operating in the QIC-11, QIC-24, QIC-120, or QIC-1S0 format, the drive is
in the explicit format mode.
In READ Operation, the drive only recognizes the selected Explicit Mode. READ commands
on all other formats are terminated with a Check Condition and a Sense Key of Blank Check.
In WRITE Operation, the drive only writes in the selected Explicit Mode. If the installed
cartridge does not support the selected Explicit Mode, the WRITE command terminates with
a Check Condition and a Sense Key of 05h Illegal Request or 07h WRITE Protect. If the
Selected DenSity Mode is a 04h or OSh in a 125S or a 150S, the write operation terminates with
OSh Illegal Request. If the cartridge cannot support the selected Density Code, 07h WRITE
Protect is set.
The reason for a WRITE Protect Sense Key is that this error code directs the user to remove the
cartridge to find that the wrong cartridge was used.
If a MODE SELECT is issued to change the Density Code, this change is not reported in a
MODE SENSE until a write or read operation is completed.
5.21.5.4 Number of Blocks. Bytes 1 to 3
This field is set to all zeros indicating that all logical blocks have the format specified in the
Density Code field.
5.21.5.5 Block Length, Bytes 5 to 7
This field is set to OOh, 02h, OOh indicating a fixed block length of 512 bytes.
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