Re: Averlogic AL250 and scan doubling

"Keith M" <keithvz@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:j69Hj.12$p97.9@xxxxxxxxxxx
Paul Carpenter wrote:

For a fixed input to LCD you will have to use NTSC YUV mode and note
that the effective 24 bit colour input is cropped to 16bit colour by the
chip.
Anything non-square pixel or using 601 formats requires a CRT that
hopefully
can sync to that rate. Anything using an LCD would need register setups
to
CROP the image.

In my case I'm coming analog RGB NTSC to standard analog VGA HD15. I
think that the AL250 requires digital inputs, so I think I'd need to
front the AL250 with an AL875.

If you have RGB NTSC consider almost ANY triple Video ADC or for that matter
even 3 off TDA8702 NXP 8bit 40Mhz video ADC (available everywhere farnell
Digikey...)
These are very cheap.

Comapnion chip is TDA8703 8 bit DAC, but I generally use Fujitsu MB40760
10bit
60MHz DAC.

If you just want to line double without interpolation, it can be acheived
digitally
very simply by PLD and a selection of FIFOs or memory.

At NTSC video rates, most memorys/FIFO's can be obtained with much faster
rate than pixel rate.

> Logic Devices make various chips for digital
processing which can be
setup quite easily to do various interpolation schemes, even changing
horizontal
resolution for full image display.

Thanks for the pointer, I'll check there.

A good resource for this type of thing is the book

Video Demystified (I have first and fourth editions)
By Keith Jack (ex Brooktree engineer)

ISBN 0-7506-7622-4

Excellent. Thanks for the reference. I've actually looked at that book
before.

Thanks

Keith

If this is for experimentation building one from PLD and memories/FIFOs, is
very instructional to understanding timing and what you then require when
looking
at specs for much more integrated solutions.

To drive NTSC RGB to VGA (640x480) display I would choose either LCD with
18 bit digital interface and/or full 24 bit analog o/p for better
performance.
With PLD solution and FIFOs becomes a module you can tweak or add methods.

Look at Logic devices structures I used to use LF3330 a lot.

--
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