Viper 60s Theory Of Operation And Maintenance Manual page 141

VIPER SCSI 60, 125
& 150 THEORY OF OPERATION AND MAINTENANCE
6.3.3 Read Data (Restore) Operation
To restore data, a read command is given at the beginning of the tape, the drive starts tape
motion in search of data. When the first block is successfully read, a ready signal is inserted
and transfer of data blocks to the host begins. The drive continues to read and transmit data to
the host until the end of data on tape is found or the end of a specified block of data to be
restored is completed.
As long as the host can maintain the required data transfer rate, the drive keeps the tape in
motion. If data transfer is interrupted, the drive stops tape motion, reverses tape direction,
and positions over previously read data. This is called a read underrun. When the host can
again transfer data, the drive starts tape motion and continues to read data.
The repositioning routine generated by read underruns reduces the average data throughput.
6.4 Drive Mechanics
6.4.1 Loading Mechanism
The Viper drive loading mechanism provides endwise cartridge loading. The head is moved
from the cartridge path during insertion so the cartridge door can be opened for head
penetration. The head is then moved back into penetration position for operation.
The head support and stepper assembly are mounted on a separate, pivoted sub frame. The
subframe is linked to the front panel latch lever so the assembly is pivoted in and out of
position as the cartridge is latched or unlatched. A leaf spring stop provides accurate and
precise location of the cartridge as it is moved into operating position.
Viper drives use a damped torsion spring to apply an outward force to the cartridge for
cartridge removal. As a cartridge is inserted into the unit this spring is compressed until the
tape is latched into the drive. When the tape is unlatched by sliding the front panel latch lever
to the left, spring compression is released and ejects the cartridge partially out of the cartridge
slot. A damping system in the eject lever controls cartridge ejection speed.
6.4.2 Cartridge Loading
The cartridge is inserted into the drive as shown in Figure 6-2. The latch lever slides toward
the center of the drive engaging the latch roller and moving the head assembly into operating
position.
1. To load the cartridge move the front panel latch lever to the left detent position and
insert the cartridge. The front panel latch insures the head assembly and front latch
roller are moved out of the way in preparation for cartridge insertion.
As the cartridge is inserted, the cartridge door is opened by a cam in the tape
guide.
2. With the cartridge fully inserted, move the front panel latch lever to the right.
Moving the lever to the right swings the head assembly into operating position
and the latch rollers are moved into pOSition, forcing the cartridge against the
reference planes.
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