Chapter 6. Theory of Operation
EK–MOL80–SV. B01
6–11
When moving cartridges where the source or destination element is the picker,
each thumb must be addressed. One thumb is at element address 16 and the other
thumb is at element address 17. The SCSI commands, such as Read Element
Status and Mode Sense report back the two element addresses for the transport
element.
Two-Move Exchange
In jukeboxes, where the picker is used in single-picker mode, exchanges are
made using two moves.
The first move takes the cartridge from the drive, moves to the home slot, and
puts the cartridge in its home slot. The second move takes a different cartridge
from its home slot, moves it to the drive, and inserts the cartridge in the drive.
The following is a detailed description of the two-move exchange.
1. a) Move to the drive (destl).
b) Eject the cartridge from the drive (spin down included).
2. Grab the cartridge from the drive.
3. Move the cartridge to its home slot (dest2).
4. Put the cartridge into the slot.
5. Move to the source slot.
6. Grab the cartridge from the slot.
7. Move to the drive.
8. Insert the cartridge into the drive.
9. Spin up the drive.
NOTE
Steps 1a and 1b occur simultaneously. Both
must complete before step 2 occurs.
The two move exchange can be performed by executing these two moves:
1. Move from destl to dest2.
2. Move from source to destl.
The drive exchange time is the time it takes to execute steps 1 through 8. The
drive down time is the time it takes to execute steps 1 through 9. When using the
two move exchange, everything is performed serially. A step cannot begin until
the previous step has completed.
