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Date Posted: 09:10:48 11/12/01 Mon
Author: Alcon
Subject: Re: Which layout of Piu to build?
In reply to: sakman 's message, "Re: Which layout of Piu to build?" on 12:15:09 11/09/01 Fri

>Hey Chris,
>
>If you're building Piu 1.0, then use Dan's layout with
>the added caps and stuff.
>
>Are you going to use Scenix chips? Do you have a SX
>programmer?
>
>If you're thinking of building Dan's Experimental
>version, then you'll need to get a Scenix chip. The
>main problem with the Experimental version is the
>onboard programmer - it was never proven to work 100%
>of the time. The rest of the circuits are the same as
>the Piu 1.0.
>
>I think Dan was the only one to get the onboard
>programmer to work and lots of other guys tried but
>gave up and built a separate SX programmer.
>
>The Scenix at 50MHz should provide a nice stable
>picture without the VCXO circuit but my Scenix at
>20MHz in Turbo mode also works good.
>
>Another consideration is that if you're working on a
>GI system, the GILN18 code has not been modified to
>work on the SX 50MHz yet. It shouldn't be too hard to
>mod my GILN18 20MHz Turbo code to 50MHz but I don't
>have the time right now.
>
>Late!

I had no problems getting the Scenix programmer to work on the experimental board. There is a very specific order that you need to use to program the chip, or else you run the risk of blowing your chips and/or parallel port. The problem is that those steps really remove the original purpose of the experimental which is to allow you to have the board hooked up to your computer and VCR at the same time.

The main problem all of us had with the board, though, was that we could never get the timings to work correctly. In order to correctly lock, the code must be perfectly timed. This requires you to change the wait to a certain number of clocks, but because of variances in the 50 MHz resonators and/or oscillators the # of clocks is different for each board. Dan had gotten his working, but a couple of us could never find the correct timing. There was talk of someone writing adaptive code to dynamically change the wait, but nothing ever came of this.

I've built Dan's version of the Piu 1.0 for the 20 Mhz scenix, but have yet to program the chip as my experimental programmer no longer appears to be working.

Good luck

-Alcon

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