If you can get 15 nS RAMs, why not interleave them to get twice the
sample rate? A few bus latches and you should be good.

On 4/5/06, Philip Pemberton <philpem@dsl.pipex.com> wrote:
> OK folks - quick update on the logic analyser project...
>
>   1) I've got the triggering and bus interface Vlog code done, checked and
> tested. That just leaves the clock divider and acquisition control left to
> do.
>
>   2) I can't get any 10ns RAMs, and even if I did I doubt they'd actually be
> able to write at the full 100MHz without thoroughly violating the data hold
> time specs.
>
>   3) I can, however, get 15ns RAMs that would easily be able to handle a
> 50MHz (or probably a bit faster) sample clock. They're Cypress CY7C1021s, in
> case anyone feels like pulling the datasheet and reading it. 44-pin SOJ,
> 1.27mm pin pitch (no smaller than a SOIC). DigiKey have got the 10ns version,
> which should be OK as a substitute. No guarantees on sample rate, but I want
> 20MHz as a bare minimum, and I'm actually aiming for 50MHz.
>
>   4) I've got the equipment to do double-sided PCB manufacture, but I don't
> have anything to do plated holes with. If anyone wants to donate a few
> Multicore Copperset bail-bars and a 0.9mm pencil, I'm not going to stop them
> :). I've already got a modified centre-punch, 0.85mm drill bit and a small
> anvil, so that's most of the tools covered.
>
>   5) Construction is going to be mostly SMD but with some through hole parts
> (connectors mostly). I hate drilling holes in PCBs. Offboard connections are
> going to be USB, 9-12V power and 16-bit bus input. I estimate the final board
> size to be somewhere around Eurocard size, though with a bit of luck (and a
> lot of SMDs) I might be able to get it down to half-Eurocard.
>
>   6) Schematics will be released as-and-when. I want to get the basic
> hardware design stabilised before I release anything. Thankfully the CPLD
> should allow me to fix most Silly Bugs (tm) without cutting and rerouting
> tracks.
>
>   7) I'm using a PIC18F4550, mainly because that's the only USB PIC I've got
> in my junk box.
>
> Thanks.
> --
> Phil.                         | Kitsune: Acorn RiscPC SA202 64M+6G ViewFinder
> philpem@dsl.pipex.com         | Cheetah: Athlon64 3200+ A8VDeluxeV2 512M+100G
> http://www.philpem.me.uk/     | Tiger: Toshiba SatPro4600 Celeron700 256M+40G
> --
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--
-Randy Glenn
Computer Eng. and Mgt. Year IV, McMaster University
Regional Student Representative, IEEE Canada

randy.glenn-at-gmail.com - glennrb-at-mcmaster.ca
randy.glenn-at-computer.org - randy_glenn-at-ieee.org
http://www.randyglenn.ca

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