ADVANCE INFORMATION
VDP 3108
2.6.2. Deflection Processing
The deflection processing generates the signals for the
horizontal and vertical drive (fig. 2–27). This block con-
tains two phase-locked loops:
– PLL2 generates the horizontal and vertical timing.
Phase and frequency are synchronized by the front
sync signal. The Main Sync (MSY) signal that is gener-
ated from PLL2 is a multiplex of all display related data
(fig. 2–28). This signal is intended for use by other pro-
cessors, e.g. a PIP processor can use this signal to ad-
just to a certain display position.
– PLL3 adjusts the phase of the horizontal drive pulse
and compensates for the delay of the horizontal output
stage.
The horizontal drive circuitry uses a digital sine wave
generator to produce the exact (subclock) timing for the
drive pulse. The generator runs at 1 MHz; in the output
stage the frequency is divided down to give drive-pulse
period and width. In standby mode, the output stage is
driven from an internal 1 MHz clock that is derived from
the 20 MHz main clock oscillator and a fixed drive pulse
width is used. When the circuit is switched out of standby
operation the drive pulse width is programmable. The
horizontal drive uses a high voltage (8V) open drain out-
put transistor.
phase
comparator
&
lowpass
DCO
PLL3
sinewave
generator
DAC
&
LPF
1:64
&
output
stage
H
flyback
H
drive
Standby clock
FSY
main
sync
interface
phase
comparator
&
lowpass
DCO
line
counter
composite
sync
generator
CSY
MSY
main
sync
generator
VDATA
vertical
serial
data
display
timing
PLL2
blanking, clamping, etc.
clock & control
E/W
correction
PWM
15 bit
sawtooth
PWM
15 bit
V
flyback
E/W
ouput
V
output
Fig. 2–27: Deflection processing block diagram
input
analog
video
MSY M1 M2
(not in scale)
timing reference for PICTURE bus
– chroma multiplex sync
– active picture data after xxx clocks
Fig. 2–28: Main sync format
MICRONAS INTERMETALL
M1
line
[0]
line
[7]
Parity
M2
line not not not not not
[8] used used used used used
F
V Parity
V: Vert. blanking
0 = off
1 = on
F: Field #
0 = Field 1
1 = Field 2
line: Field line #
1...N
21