MC44002P View Datasheet(PDF) - Motorola => Freescale
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MC44002P Datasheet PDF : 40 Pages
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MC44002 MC44007
flag is effectively saying that the vertical timebase is out of
lock need not be a cause for major concern, since the
horizontal timebase will still be locked to the signal, and has
its own flag – “Horizontal out of lock”. The vertical countdown
and horizontal lock flags both perform an independent test for
the presence of a valid signal. A logical OR function can be
performed on the two flags, such that if either are present
then by definition a valid signal is present.
The vertical oscillator has end-stops set at two line-count
decodes as given below:
50 x 625 / 740 = 42.2 Hz (min)
50 x 625 / 448 = 69.8 Hz (max)
These figures assume that the horizontal timebase is
running at 15,625 Hz. When the vertical timebase is in
Injection Lock mode, the line counter reset is inhibited so that
it ignores any sync pulses before a count of 448 is reached.
This prevents any possible attempted synchronization in the
middle of the picture. If the count reaches 740 lines, then
there is an automatic reset which effectively sets the lower
frequency limit. The choice of these limits is a compromise
between a wide window for rapid signal capture and a narrow
window for good noise immunity.
It is also possible to run the timebase in 2.0 V mode as
there are decodes for 100 Hz (2 x 50 Hz) operation with
upper and lower limits in proportion. This is, of course,
intended to be used in conjunction with field and frame
memory stores. The similar decodes which would be
necessary to allow 120 Hz (2 x 60 Hz) operation have not, for
the present, been implemented. Finally, the timebase can be
forced into a count of either 625 or 525 by commands from
the MCU; in this mode the input signal, if present, is ignored
completely. If there is no signal present save for noise, then
this feature can be used to obtain a stable raster.
In the analog section, an adjustable current source is used
to charge an external capacitor at Pin 6 to generate a vertical
ramp. The amplitude of the ramp is varied according to the
current source (Height), and is automatically adapted when
the 525 standard is recognized by multiplying by 1.2. The
Linearity control is achieved by squaring the ramp and either
adding or subtracting a portion of it to the main linear current.
In addition, a correction current, depending on the level of
anode current, is applied in the sense of oppose a change of
picture height with EHT (Breathing).
The final ramp with corrections added is then passed to a
driver/amplifier and is output at Pin 7. The vertical ramp can
be used to drive a separate vertical deflection power circuit
with local feedback control. Vertical “S” Correction will then
be made using fixed components within the feedback loop of
the power op amp. The vertical position can be adjusted
under MCU control – this is achieved by varying the dc output
level at Pin 7. The vertical amplitude can be reduced to 75%
of its original value (bit VDI) to make possible the display of a
16:9 picture on a 4:3 screen.
The reference ramp is squared to provide a pin-cushion
correction parabola, developed across an external resistor at
Pin 8. The parabola itself is squared, giving an independent
fourth order term (Corner Correction) whose level can also
be varied; this is then added as a further modifying term to
the E-W output. This latter correction is used for obtaining
good corner geometry with flat-square tubes. A variable dc
current is added to the parabola to effect a width control.
Using a suitable power amplifier and a diode-modulator in the
line output stage, the parabola may be used for E-W
correction and dynamic width control. A further control is
provided to shift the center point of the parabola up and down
the screen (Parabola Tilt).
All of the vertical and horizontal signals are adjustable via
6-bit words from the MCU, and stored in latches. The
adjustment controls available are:
Vertical Amplitude/Linearity/Breathing Correction/Position
Parabola (E-W) Amplitude/Horizontal Amplitude/
Corner Correction, and Parabola Tilt
The Anode Current Sense at Pin 9 is also used as a beam
current monitor. Two thresholds may be set, by the
manufacturer, using external components. The first threshold
sets a flag to the processor if beam current becomes
excessive. The MCU could, e.g., reduce brightness and/or
contrast to alleviate the condition. The second threshold sets
a flag warning of an overload condition where the CRT
phosphor could be damaged. If such a condition were to
arise, the processor would be programmed to shut down
the PSU.
The vertical blanking lines may be selected by means of a
bit from the MCU for either the 525 or 625 standard. The
interlace may also be suppressed again under the control of
the processor (bits ICI, IFI).
MOTOROLA ANALOG IC DEVICE DATA
21
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