5190/5194 Modular Tape Subsystem Manual

Operating the Cartridge Tape Drive and ACL
5190/5194 Modular Tape Subsystem Manual—426878-002
4-7
Controls on the ACL Front Panel
Tape Position LEDs
Seven amber LEDs form a horizontal line at the top of the control panel and indicate
the tape position. The BOT (beginning-of-tape) LED lights when the tape is completely
rewound. As tape moves through the drive, neighboring LEDs to the right light
sequentially to indicate the tape position. When the tape is moving, the rightmost LED
that is lit flashes on and off; when the tape is stopped, the rightmost LED that is lit
remains lit without flashing. (This LED sequence is the only sequence for the 5190
tape drive.)
The 5194 tape drive uses the same LED sequence for writing or reading 18-track data
to the physical end of the tape. The 5194 tape drive then reverses the sequence as it
continues writing or reading the additional 18 tracks of data (resulting in 36 tracks of
data) back to the physical beginning of the tape. (For the 5194 tape drive, the physical
beginning of the tape is also the end-of-tape position.)
End-of-Tape LED Sequence for the 5190 Tape Drive
When the cartridge reaches the physical end of the tape in a 5190 tape drive, it also
reaches the end-of-tape (EOT) position. All seven tape position LEDs are lit. At this
point, the 5190 tape drive is finished writing or reading 18-track data. When the 5190
tape drive is at EOT, the tape must be rewound or repositioned to an earlier point on
the tape.
End-of-Tape LED Sequence for the 5194 Tape Drive
When the cartridge reaches the physical end of the tape in a 5194 drive, it has reached
only the halfway point (sometimes called wrap 1) for writing or reading data. All seven
tape position LEDs are lit. At this point, the 5194 tape drive continues writing or
reading 18-track data (sometimes called wrap 1) for a total of 36 tracks, back to the
physical beginning of the tape.
As tape moves through the drive (back toward the physical beginning of tape),
neighboring LEDs to the left become unlit sequentially (starting with the BOT LED at
the far left). When the tape is moving, the leftmost LED that is lit flashes on and off;
when the tape is stopped, the leftmost LED that is lit remains lit without flashing. For
the 5194 tape drive, when the cartridge reaches the end-of-tape (EOT), the EOT LED
is the only LED lit. When the 5194 tape drive is at EOT, the tape is also at the physical
beginning of the tape. For that reason, whenever you write the first record at BOT you
might notice the EOT LED flash on briefly.
You’ll also notice that rewind time is minimal if the read or write operation uses the
entire tape.
A flashing (blinking) tape position LED indicates that tape is in motion.