VDP 313xY
ADVANCE INFORMATION
2.12.5.EHT Compensation
2.13.Reset and Power On
The vertical waveform can be scaled according the
average beam current. This is used to compensate the
effects of electric high tension changes due to beam
current variations. EHT compensation for East/West
deflection is done with an offset corresponding to the
average beam current.
Reset of most VDP 313xY functions is performed by
the RESQ pin. When this pin becomes active all inter-
nal registers and counters are lost. When the RESQ
pin is released, the internal reset is still active for 4 µs.
After that time, the initialization of all required registers
is performed by the internal Fast Processor.
The VDP 313xY has clock and voltage supervision cir-
cuits to generate a stable HOUT signal. The voltage
supervision activates an internal reset signal when the
supply for the digital circuits (VSUPD) goes below
~2.5 V for more than 50 ns. This reset signal is
extended by 50 µs after VSUPD is back again.
2.12.6.Protection Circuitry
– Picture tube and drive stage protection is provided
through the following measures:
– Vertical flyback protection input: this pin searches
for a negative edge in every field, otherwise the
RGB drive signals are blanked.
After power on or reset the HOUT generation is
switched to a freerunning mode with a fix duty cycle of
50 %. For normal operation the EHPLL bit has to be
set first. During the switch the actual period of HOUT
can vary by up to 1 µs.
– Drive shutoff during flyback: this feature can be
selected by software.
– Safety input pin: this input has two thresholds.
Between zero and the lower threshold, normal func-
tioning takes place. Between the lower and the
higher threshold, the RGB signals are blanked.
Above the higher threshold, the RGB signals are
blanked and the horizontal drive is shut off. Both
thresholds have a small hysteresis.
Reset
– The main oscillator and the horizontal drive circuitry
are run from a separate (standby) power supply and
are already active while the TV set is powering up.
4µs
approx. 60µs
Internal
Reset
Initialization
Fig. 2–26: External Reset
28
Micronas
MICRONAS [ MICRONAS ]
