Sony TVP-08, Training Manual

Page: 97 / 139

89
VDSP
Overview
IC512 is the VDSP or Vertical Digital Signal Processor. This IC outputs
the V Drive, Pin, AFC and VTIM signals. It receives data over the I²C bus
to manipulate these waveforms. Changing these waveforms varies many
of the picture adjustments, including VSIZE, HSIZE, VPOS, UPIN and
LPIN, as well as others. This IC consists of four basic parts - they are the
VCO, Countdown Processor (CDP), Digital Signal Processor (DSP) and
DAC.
VCO
The VCO is needed by the CDP and DSP to provide a stable clock. An
internal VCO uses C678, which is connected to IC512/5 VC1, to create a
VCO. This VCO is synchronized with the ½ H signal that is input at IC512/
16 H In. The two signals are phase compared internally and the output of
the phase comparator exits IC512/18 PHA. An op amp internal to IC508
VDSP filters this output using C675 and R757, which are connected to
pins 8 and 7. The voltage created by this circuit is used internally to
control the frequency of the VCO.
CDP
The countdown processor consists of an ALU, RAM and ROM and oper-
ates on an internal program stored in its ROM. The CDP determines
which type of system is being used, 50 or 60 Hz, and outputs various
counts according to its program. It also receives an input at IC512/22
VSY from the VS signal. This syncs the counting with the vertical sync
from the incoming video. This circuit outputs the VTM signal at IC512/36
VTM. This signal will be used as VBLK and inverted and used as VP.
Notice that R645 is listed in the service manual with a # symbol next to it.
If you see # next to a component in a manual, this means that this compo-
nent is not mounted on the board. The other outputs from the CDP are
input to the DSP section of IC512.
DSP
The DSP consists of an ALU, multiplier, RAM and ROM. It uses the count
information it receives from the CDP and its own internal program to gen-
erate the vertical deflection sawtooth, the Pin or parabolic signal and the
AFC compensation signal. This section also receives data to manipulate
these waveforms for the picture adjustments stated earlier. These out-
puts are then applied internally to three 1-bit D/A converters.
DAC
IC512 VDSP contains three D/A converters, two with low pass filters and
one without. The DAC without the low pass filter outputs the AFC wave-
form. Since this is a 1-bit DAC and its output is not being passed through
an LPF, the signal at IC512/24 is a high frequency signal resembling a
square wave. This signal is output to the H Jungle circuit, which contains
the LPF.
The vertical deflection sawtooth is output from a DAC into a LPF. This
LPF uses C644 and C651, which are connected at IC512/44 and 45. This
LPF outputs complimentary signals from IC512/47 and 48 into IC514/6
and 5. The output from IC512/1 Saw is the sawtooth signal and is input
along with the output from IC514/7 into IC514/3. IC514/1 is the buffered
output called V Drive that will be used to drive the vertical output circuit.
The parabola or pincushion signal is output from a DAC into a LPF. This
LPF uses C667, C660 and C657, which are connected to IC512/12, 13
and 14. IC512/11 Par produces an analog output that is used as the input
to the Pincushion correction circuit.
IC512/24
AFC Out
2V 400ns