[This was a post on a device that would check for three output levels, rather than just two: "0", "1" and "somewhere in between, so neither." To avoid derailing this discussion, I've moved it to its own thread: A "Poor Man's Logic Analyzer" With TTL Threshold Detection. ]

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Curt J. Sampson - github.com/0cjs

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

One could even go a step further here, and test against three voltage thresholds: TTL/CMOS low, TTL high, and CMOS high.

These could be processed into a 2-bit code, synchronised with a clock and trigger, and recorded into a sample buffer, which is the essence of a logic analyser, but with some basic analogue-domain information included. If the thresholds can be adjusted by hand, this can also be made useful in an LVCMOS context.

To avoid derailing this thread too much, I've reposted my Octal TTL Logic Probe post as the head of a new thread, and added my further responses there (as has, already, Garth; thanks Garth!).

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Curt J. Sampson - github.com/0cjs