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Advice on determining a logic analyzer for use with 1980s synthesizers. TLA715?
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tggzzz:

--- Quote from: artag on June 15, 2024, 09:17:52 am ---There are lots of options in terms of digital and analogue capture. Get the deepest memory you can afford but be aware you'll sometimes limit the capture to keep the display time down. On these parallel bus processors you'll be using it in state mode though, which is far more efficient for memory use.

--- End quote ---

Memory efficiency is relatively unimportant, especially now memory is so cheap.

What is important is being able to ignore rubbish, so you can concentrate on what is important. That's why state-based arm/trigger/filter is so important: it saves your time. If you don't capture the crap, there's nothing to ignore.

Alternatively: good luck finding the "wrong" bit in 10MS of 32 bit captures.
nctnico:

--- Quote from: tggzzz on June 15, 2024, 04:58:11 pm ---
--- Quote from: artag on June 15, 2024, 09:17:52 am ---There are lots of options in terms of digital and analogue capture. Get the deepest memory you can afford but be aware you'll sometimes limit the capture to keep the display time down. On these parallel bus processors you'll be using it in state mode though, which is far more efficient for memory use.

--- End quote ---

Memory efficiency is relatively unimportant, especially now memory is so cheap.

What is important is being able to ignore rubbish, so you can concentrate on what is important. That's why state-based arm/trigger/filter is so important: it saves your time. If you don't capture the crap, there's nothing to ignore.

Alternatively: good luck finding the "wrong" bit in 10MS of 32 bit captures.

--- End quote ---
OTOH: if you don't know what to look for, doing offline analyses on a long capture using advanced search methods (which modern logic analysers do provide) is way more efficient compared to doing lots of captures while trying to kind of narrow down the correct trigger condition. On top of that, a long capture also allows to do other analysis / sanity checks on the data being captured which is simply impossible to do with limited memory depth. Quite often you can find interesting information that way you would have missed otherwise.
TomKatt:
But if you know what makes it “wrong”, you could always filter out the noise.

If you don’t know what makes it “wrong”, you can’t set up a trigger to begin with.

And sure - I’d take a hardware trigger over not, all other things being equal.
tggzzz:

--- Quote from: TomKatt on June 15, 2024, 05:30:50 pm ---But if you know what makes it “wrong”, you could always filter out the noise.

If you don’t know what makes it “wrong”, you can’t set up a trigger to begin with.

And sure - I’d take a hardware trigger over not, all other things being equal.

--- End quote ---

That is true whenever/wherever the analysis is done.

Blindly capturing everything is suboptimal and is rarely necessary. More often - and more profitably - you have a concept of the problem's cause and consequences, and filter based to observe your hypothesis

It is much more than just a trigger, of course. With appropriate filtering you can capture only the sequence of instructions fetched, or read/write to an address range, or latencies between an interrupt occurring and the first instruction of the ISR being executed, etc, etc, etc. That's made easier with old processors since all that information appears on external pins.
tggzzz:

--- Quote from: nctnico on June 15, 2024, 05:17:18 pm ---
--- Quote from: tggzzz on June 15, 2024, 04:58:11 pm ---
--- Quote from: artag on June 15, 2024, 09:17:52 am ---There are lots of options in terms of digital and analogue capture. Get the deepest memory you can afford but be aware you'll sometimes limit the capture to keep the display time down. On these parallel bus processors you'll be using it in state mode though, which is far more efficient for memory use.

--- End quote ---

Memory efficiency is relatively unimportant, especially now memory is so cheap.

What is important is being able to ignore rubbish, so you can concentrate on what is important. That's why state-based arm/trigger/filter is so important: it saves your time. If you don't capture the crap, there's nothing to ignore.

Alternatively: good luck finding the "wrong" bit in 10MS of 32 bit captures.

--- End quote ---
OTOH: if you don't know what to look for, doing offline analyses on a long capture using advanced search methods (which modern logic analysers do provide) is way more efficient compared to doing lots of captures while trying to kind of narrow down the correct trigger condition. On top of that, a long capture also allows to do other analysis / sanity checks on the data being captured which is simply impossible to do with limited memory depth. Quite often you can find interesting information that way you would have missed otherwise.

--- End quote ---

The low end modem LAs have very restricted functionality w.r.t. filtering and triggering. Decent modern LAs are fine, as are old LAs from that period, e.g. >HP163x.
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