AT&T 3B2/300 Technical Reference Manual page 542

- - - - - - - - - - - - - - - - - - - - - - - - - - FUNCTIONAL DESCRIPTION
TO/FROM
CM195H
CARTRIDGE
TAPE
CONTROLLER
CARD
/
-
READ DATA
READ
-
-
-
AMPLIFIER
h
INDEX MARK
DETECTION
AND
-
GENERATION
LOGIC
WRITE DATA
WRITE GATE
WRITE
WRITE PROTECT
LOGIC
f
ENABLE
-
DIRECTION
-
-
HI SPEED
-
STEP
-
-
DIRECTION
MOTOR ON
CONTROL
-
LOGIC
TRACK 0
H
ACCESS
I
INDEX
INDICATOR
-
READY
H
DOORLOCK
I
SOLENOID
- -
'
DRIVE SELECT
STREAM
SIDE SELECT
SELECT
LOGIC
"
.......
-'
HEAD
I
- I
...
...
±(3
DRIVE
MOTOR
EOT/BOT
SENSOR
HEAD
POSITIONING
STEP
MOTOR
WRITE
PROTECT
SENSOR
Figure 3-90: 23-Megabyte Cartridge Tape Drive - Functional Block Diagram
Tape Drive
Tape motion is via a capstan driven by a 3-phase, brushless DC motor. The motor speed is
controlled by an onboard microprocessor using pulse-width modulated signals. Tape speed is 78 inches
per second.
Read/write head positioning is done by a stepper motor controlled by the control logic in response
to the Drive/Side Select signals. The read/write head is always returned to a home position before
positioning the head to a new stream. This technique provides optimum positioning accuracy. Each
position step requires 200 milliseconds.
FUNCTIONAL DESCRIPTION 3-289