TM
11-5835-243-34/EE641-AA-MMl-010/E154
MTT/TO
31S3-4-110-1
2-2. Digital Read Write Circuit Card Assembly
c. Motor current feedback amplification.
d. Integrate tape transport sensor signals.
The tape transport contains three identical, in-
Upon insertion of the tape cartridge into the tape
terchangeable digital read/write circuit cards (A1,
transport, the magnetic tape is automatically
A2, A3). Each circuit card contains three identical
pressed against the read/write head, the tape guide
read/write amplifier sections, providing a total of
posts, and the capstan. The capstan shaft drives the
nine digital read/write channels. The functions of
tape contained within the cartridge. Proper tape
the read/write circuit cards follows:
tension is maintained in either direction and at all
a. Buffer incoming NRZ format digital data.
speeds by an elastic belt in the cartridge. The
b. Convert NRZ to NRZ1 format.
capstan is driven by dc servomotor (B1) (part of the
c. Drive the magnetic head assembly.
velocity servo loop). All tape motion is under direct
d. Amplify signals from the magnetic head
servo control. Velocity information is a voltage
assembly.
generated by the dc tachometer which is directly
e. Reconstruct the signals to digital format.
mounted on the capstan motor shaft. This voltage is
f. Reconvert to NRZ format.
continuously compared to a fixed reference, and the
g. Deskew the parallel digital data.
difference is an error signal which is amplified and
The nine incoming channels of parallel digital data
used to keep the dc motor at a constant speed.
are received by the write amplifiers and converted
During starting and stopping, a ramp voltage is
from NRZ (non-return to zero) to NRZ1 format (para
generated for the reference in order to produce
controlled acceleration and deceleration of the tape.
write amplifier in the prescribed format. The erase
In this matter precise starting and stopping is
head is energized automatically when in the write
obtained within specified inter-record gaps.
mode, providing increased data reliability when
writing over old data. When in the read mode, the
2-5. Magnetic Tape Cartridge Functional
read head senses the magnetic signals on tape.
Description
These signals are amplified, peak-detected and
a. Forward Tape Motion. In the tape forward
shaped by the read section of the read/write circuit
mode, belt idlers rotate counterclockwise and the
card. A common clock, generated by the control
reels rotate clockwise. The initial tension in the
logic circuit card, is used by the deskew circuit to
elastic belt, created by the elongation of the belt at
desynchronize all data output channels. The tape
the time of assembly into the cartridge, pulls the
transport can synchronously read and write at
floating pressure roller into the supply and take-up
speeds up to 22.5 ips. In addition, a search speed of
reels creating two pinch zones `A' and `B' (fig. 2-2).
up to 45 ips is provided in the forward and reverse
The resistance of the belt to elastic deformation at
directions.
point `A' produces a higher tension in the belt be-
2-3. Control Logic Circuit Card Assembly
tween points `A' and `B' than in the section from `A'
to `D'. Additional resistance to deformation at point
The control logic circuit card assembly (A4) receives
`B' creates an even higher tension between `B` and
input/output commands and provides the logic
`C' than in section `AB.' This dual difference in
circuits to control tape motion, read/write enables,
actual belt tension causes the belt to be thinner in
and to generate tape transport status signals.
section `BC' than it is in section `DA'. Since there is
2-4. Servo Control Circuit Card Assembly
no slippage between the belt and the magnetic tape
in either section, the mass transfer rate of the belt
The servo control circuit card assembly (A5), in
must be equal in both. Hence, the velocity of the belt
conjunction with the power amplifier assembly (A9),
in section `BC', where the belt is thinner, must be
and the capstan motor assembly (B1), forms a
larger than in section `DA', where the belt is thicker.
velocity servo control of the tape speed. The func-
The difference in peripheral belt velocities gives the
tions of the servo control circuit card assembly are
tape on the take-up reel a higher peripheral velocity
as follows:
than the tape on the supply reel. Since the take-up
a. Provide a dc reference voltage for tape speed
reel is trying to wind tape faster onto the take-up
control.
reel than is unwound from the supply reel, the free
b. Generate a voltage ramp for controlled tape
length of tape between the two reels is stretched,
start and stop.
creating a tension in this portion of the tape.
2-3
