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From:   John Payson
Sent:   Thursday, April 17, 1997 6:26 PM
To:     'pic microcontroller discussion list'
Subject:        RE: NTSC Video

|Would someone be kind enough to point me to some references on NTSC.
| Specifically how to generate it and what chips to use.

Depending upon your display requirements (how much stuff you have
to display, color, etc.) and what else the PIC has to be doing, you
may fall into any of four scenarios:

[1] "Dirtball": If your requirements are sufficiently modest, you
    may be able to get by with just the PIC, some resistors, and a
    capacitor.  This would be the case, for example, if you just
    wanted to generate a few large characters on an otherwise blank
    screen and if you didn't have anything else time-critical to
    worry about.

[2] Minimal help: Adding a couple of chips or a PLD to the PIC can
    improve considerably its ability to display things; you could
    probably get 20-30 characters on a line with this technique
    pretty easily, though at considerable expense of code space and
    RAM.

[3] Self-built video subsystem: adding some more chips and/or a FIFO
    will allow you to display a fair amount of video, but at some
    considerable expense in CPU time.  Using an 8K fifo and a PLD as
    the only support components, you could probably display a nice
    screenful of text [if most of the text was stored in EPROM; the
    PIC's RAM wouldn't hold all that much].

[4] External video subsystem: you may opt to use one of a few chips
    that generate video entirely themselves.  Commodore used to make
    a really nice chip for that purpose (the 80-column chip in the
    C128) but AFAIK the chip no longer exists anywhere in quantity.
    Otherwise, Philips et al make a variety of such things.

What do you need to display?  If you supply more information, I can
help you place your task in one of the four roles.

I am using the PIC to compute average speed and fuel flow rate. A second
PIC or better suited component can be used to generate the display. Video
quality is a plus, so I would say I am in group 3 or 4.

The television already exists in the application, so NTSC is preferred
to an LCD or other display.

I'd love to find a book or web site that discusses the operation of NTSC.

Thanks,

Chris


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