Viper 60s Theory Of Operation And Maintenance Manual page 125

VIPER SCSI COMMANDS
5.24 PREVENT/ALLOW Media Removal (1 Eh)
Because the Viper drive does not physically prevent the removal of the cartridge during those
times when the tape is moving in the drive, the front panel LED indicates when removal is
allowable.
If the LED is ON (PREVENT command), cartridge removal is not allowed. If the media is
removed when the LED is ON, the Unit Attention Condition is set. If the LED is OFF (ALLOW
command), media removal is allowed. If the cartridge is removed while the LED is OFF, no
Unit Attention is set. If the PREVENT command is issued, the LED is always ON even at BOT,
and then media removal even at BOT causes the Unit Attention Condition to be set. After a
Reset, the default state of the drive is in the ALLOW command mode.
NOTE: The Prevent/Allow command can only be issued at BOT.
5.24.1 PREVENT/ALLOW MEDIA REMOVAL
C~mmand
Descriptor Block
BITS
7 6
5
4 3 2 1 0
BYTE
0 0 0 0 1 1 1 1 0
1 0 0 0 0 0 0 0 0
2 0 0 0 0 0 0 0 0
3
0 0 0 0 0
0
0 0
4 0 0 0 0 0 0 0
PRVNT
5 X X
0 0 0 0 Flag Link
5.24.2 Command Descriptor Block Field Description
The PRVNT (prevent) bit, Byte 4, Bit 0, specifies whether the front panel LED should be
turned on
(1)
or turned off
(1)
when at BOT.
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