John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.comThe Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.comOff Topic, but 74FXXX did work. You just needed separate ground and power
planes and serious decoupling, virtually requiring 4 layer boards which
weren't all that common back then.
ABT and other recent logic is much better today.
Early Altera CPLDs were worse for ground bounce than F chips. On the early
600, 900 1200 series Altera was recommending gray code counters (only 1 bit
transitions at a time) because their chips couldn't handle transition of an
8 bit counter from 11111111 to 00000000 without internal glitching.
I found a similar problem on a 1990ish AMI/Gould PLD. Data glitch was
pattern sensitive. I had to trace circuitry through half a dozen full
height racks to solve that one. Switched to a similar Lattic part - problem
solved.
John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.comThe Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com > -----Original Message-----
> From: Paul Schreiber [mailto:synth1@...]
> Sent: Saturday, August 07, 2004 11:37 AM
> To: motm@yahoogroups.com; Bob Colwell
> Subject: Re: [motm] Re: YASDWB
>
> 74Fxxx logic ∗never∗ worked. I think many TTL design carrers were derailed
> by
> those awful things.
>
> The VC Pulse Divider will have 74ABT244 drivers on the outputs. Hardly any
> ground bounce at all (ground bounce causes severe under-shoot in TTL
> edges).
>
> Paul S.
> going digital this weekend
>