(5-7-5. CD-17 Board)
3.
Capstan Rotation Detection
Based on the CAPSTAN
FG A and B signals converted to the
TTL level in the capstan velocity loop, the capstan's rotational
direction, speed and duration are detected and these are sent to
the CPU in the form of data which indicate the status of the
capstan.
Rotational
Direction
Detection
The
rotational
direction is detected by using the fact
that the CAPSTAN
FG A signal phase advances in the FWD
mode and the CAPSTAN
FG B
phase advances in the
REV mode. In order to compensate
for errors with reverse
rotation, detection is made using two D-type flip-flops (IC2C-6,
IC4M-l).
TP6
TTL
FG A
FWD
~
TP7
TTL
FG B
"L"----------
z
o
~
«
IT:
w
CL
o
LL
o
>-
IT:
o
w
I
~
tri
IC2C-6
IC4M-1
" L"
_
Rotational
Speed Detection
The rotational
speed of the capstan is detected by IC5K
The CAPSTAN
and
time difference
from IC4N-
6 are sampled by the 0.4 microseconds
clock pulses from IC4S-6
and is sent to the
as the data which indicate the
rotational speed The FG frequency differs according to the tape
TP6
TTL
FG A
TP7
TTL
FG
8
IC4N-6
tC4C-13
CAP VELO
REQUEST
TAPE SPEED~ 0.8
IC51-10
CAP VELO
GATE
TP16
TAPE SPEED=0.8toO.6
----
........
I C51-10
CAP VELO
GATE PULSE
TP16
_____
ruLS1.JIloooo-
_
TAPE SPEED:§:"0.6
IC51-10
CAP VELO
GATE PULSE
TP16
____
----orulo.....-.
_
Duration
Detection
For compensating
for the
and mechanical
of the
CAPSTAN FG A and B signals, the time equivalent
to 2 FG
duration with a tape
of less than l x
or the time
equivalent to 32 FG duration with a tape speed of over l x speed
is
the 3.2 microseconds
clock
from IC4S-4
and this information
is sent as the data indicating the capstan's
duration
to the
SERVO SYSTEM
5-7-8
BVH-2000( U/C)/PS/PM
BVH-2180(U/C)/PS/PM
Summary of Contents for BVH-2000
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