Author Topic: Which logic analyzer for FPGA work up to 300-400 Mhz  (Read 8298 times)

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Offline suspensionTopic starter

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Which logic analyzer for FPGA work up to 300-400 Mhz
« on: January 06, 2023, 05:59:57 pm »
I do quite a lot of FPGA work and use internal chip scope from Xilinx to inspect internal signals. The biggest issue with this approach is that any change requires a re-synthesis/implementation of the design which can take 5-15 minutes for complex designs. Therefore, I am evaluating a dedicated logic analyzer with good trigger capabilities and some support for protocol decoding.
My budget is 500USD. Used ones are OK.
Two main options are either to buy a used old HP/Agilent/Tek from ebay or buy a new USB based one from ebay/Amazon/Aliexpress. I prefer the first option but wanted to check others' opinions as well. Thoughts?

 

Offline nctnico

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #1 on: January 06, 2023, 06:30:32 pm »
I'd get an old Tektronix like the TLA700 series (TLA715 for example). The triggering abilities on these are awesome and they have 56 bit timestamps on all samples so you can use an acquisition mode that only records where certain signals change allowing for really long recordings without wasting memory on useless information. In most cases I don't bother to setup a specific trigger.

IMHO the TLA7AA4 acquisition modules are the nicest option because there also have 4 analog outputs that allow to watch any connected signal using an oscilloscope. The probes that use an elastomer connector are really cheap and some have posted break-out board designs for these probes on this forum. The TLA7AA4 modules can be hacked to allow full memory bandwidth and maximum state frequency in a very simple way by sending a couple of SCPI commands.

You could use a scope hooked up to the analog outputs to do protocol decoding. I have written some limited protocol decoders (I2C and SPI IIRC) for the TLA700 series in the past as plugins but I have not managed to get these to work well with the most recent version of the TLA700 software.
« Last Edit: January 06, 2023, 06:32:12 pm by nctnico »
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Offline mtk

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #2 on: January 06, 2023, 06:35:48 pm »
Probably you could look at DSLogic U3Pro16 and DSLogic U3Pro32 https://www.dreamsourcelab.com/product/dslogic-series/ – 16/32 digital channels. USB 3.0 interface, Up to 1GHz sample rate, Up to 2Gbits hardware memo. The current price for 16-channel version on DreamSourceLab shop is 299 USD https://www.dreamsourcelab.com/shop/logic-analyzer/dslogic-u3pro16/. The software – DSView https://github.com/DreamSourceLab/DSView is not bad, based on sigrok – open-source. Has some issues, but there are people that provide technical support. And it will support much more decoding protocols in comparison to old alternatives.
« Last Edit: January 06, 2023, 06:49:55 pm by mtk »
 

Offline nctnico

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #3 on: January 06, 2023, 06:58:33 pm »
But the problem with the typical USB logic analysers is that they don't have the elaborate triggering posibilities of a real logic analyser. The ones from Tektronix (and I assume HP/Agilent) have trigger systems that are fully programmable where you can use timers, event counters, states, etc. Basically you can program these using a set of conditions that allow to capture extremely elusive bugs / events. At some point deep memory just runs out.

Or put differently: if you have an oscilloscope with digital inputs (=MSO) + decoding, you are probably better off using that because it also allows to see the digital signals in realtime. Having a USB logic analyser doesn't add much value to your toolbox if you have an MSO.
« Last Edit: January 06, 2023, 07:00:12 pm by nctnico »
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Offline RoGeorge

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #4 on: January 06, 2023, 07:00:01 pm »
I do quite a lot of FPGA work and use internal chip scope from Xilinx to inspect internal signals. The biggest issue with this approach is that any change requires a re-synthesis/implementation of the design which can take 5-15 minutes for complex designs.

Most of the debugging should happen in simulation.

Chipscope ILA is a last resort and only rarely used.  Clipping probes at 300-400MHz most probably will ruin the signal integrity and make one chasing ghosts.  Even if possible to clip the probes, it will take more time to physically attach the probes and to operate the external LA, than the 5-15 minutes needed for a new Chipscope setup.  An external LA won't save time, quite contrary.

Can you give a few examples with what kind of signals you want to probe and/or decode?
« Last Edit: January 06, 2023, 07:18:23 pm by RoGeorge »
 
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Offline nctnico

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #5 on: January 06, 2023, 07:05:07 pm »
Most of the debugging should happen in simulation.

Chipscope ILA is a last resort and only rarely used.  Clipping probes at 300-400MHz most probably will ruin the signal integrity and make one chasing ghosts.  Even if possible to clip the probes, it will take more time to physically attach the probes than to operate the external LA, than the 5-15 minutes needed for a new Chipscope setup.  An external LA won't save time, quite contrary.
Not really. In an FPGA design you typically have dedicated outputs to connect an LA to. In my designs I have a mux (somehow controlled) that allows to look at various internal signals. With all the modules together (and some internal software running in a softcore), simulation will be too slow. Simulation only takes you so far as verifying a module works but with the whole thing integrated and external signals in play, it is a different world and sometimes you need to know more about why & how something isn't working as expected.

A logic analyser probe typically allows you to connect to signals with minimal disturbance if you hook it up using a special footprint that matches the probe. It is like having 16 or 32 active FET probes in a single package. For one project I bought an FMC connector breakout board to connect my logic analyser to the signals between the mainboard and a module. Works like a charm. See this topic: https://www.eevblog.com/forum/testgear/tla7aa4-p6860-probe-artwork/
« Last Edit: January 06, 2023, 07:10:17 pm by nctnico »
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Offline mtk

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #6 on: January 06, 2023, 07:50:25 pm »
But the problem with the typical USB logic analysers is that they don't have the elaborate triggering posibilities of a real logic analyser. The ones from Tektronix (and I assume HP/Agilent) have trigger systems that are fully programmable where you can use timers, event counters, states, etc. Basically you can program these using a set of conditions that allow to capture extremely elusive bugs / events. At some point deep memory just runs out.

So the real logic analyzer are Tektronix and HP/Agilent ? For your information an USB logic analyzer can offer much more recording memory and it is quite questionable in most of the cases if timers, event counters, states … are need it at all. But in contrast from Tektronix and HP/Agilent probably those functions can be added.
 

Offline tggzzz

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #7 on: January 06, 2023, 08:56:15 pm »
A decent logic analyser will have very powerful facilities for arming, triggering, and filtering the inputs. Those enable you to ignore irrelevant crap and only capture useful data. They will do that on the fly in real time, whereas a low-end LA will use post-processing.

That means very long capture memories are less important.

To give a contrived simple example, consider wanting to verify that that a pulse has a width between 100us and 200us and the period is exactly 1024us. You could set the trigger to be if the period is not 1024us or the pulse width is >200 or <100us. The high-end LA would sit there all day doing nothing until  the single trigger occurs. A low end LA would capture a buffer full of data, then post process it while ignoring the input (and missing the problem). That is analogous to a scopes dead time.
There are lies, damned lies, statistics - and ADC/DAC specs.
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Offline nctnico

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #8 on: January 06, 2023, 09:07:57 pm »
But the problem with the typical USB logic analysers is that they don't have the elaborate triggering posibilities of a real logic analyser. The ones from Tektronix (and I assume HP/Agilent) have trigger systems that are fully programmable where you can use timers, event counters, states, etc. Basically you can program these using a set of conditions that allow to capture extremely elusive bugs / events. At some point deep memory just runs out.

So the real logic analyzer are Tektronix and HP/Agilent ? For your information an USB logic analyzer can offer much more recording memory and it is quite questionable in most of the cases if timers, event counters, states … are need it at all. But in contrast from Tektronix and HP/Agilent probably those functions can be added.
You have to quantify that... The TLA7AA4 module has 32Mpts per channel. 128Mpts in quarter channel mode. And don't forget timestamped recording which I doubt USB LAs have. I have used the timestamped recording feature on my TLA715 + TLA7AA4 module to capture several frames worth of data from a TFT screen using a 500MHz sampling rate / 2ns time resolution. On top of that the TLA7AA4 has a short memory which is sampled using a sample rate of 8GHz (125ps timing resolution).

Another very usefull feature is to have something similar to segmented recording like you find on oscilloscopes. When a trigger condition is met, the TLA700 series can capture a chunk of samples and then wait for the next trigger. Again, this allows for spanning timeframes that you'll never be able to achieve using a logic analyser that can only do a single shot.

Bottom line: the USB logic analysers are nice for doing protocol decoding and light logic analysis tasks but they are absolutely not a replacement for a real logic analyser. Besides that, real logic analysers can be bought from Ebay for peanuts.
« Last Edit: January 06, 2023, 09:15:48 pm by nctnico »
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Offline tggzzz

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #9 on: January 06, 2023, 10:40:14 pm »
But the problem with the typical USB logic analysers is that they don't have the elaborate triggering posibilities of a real logic analyser. The ones from Tektronix (and I assume HP/Agilent) have trigger systems that are fully programmable where you can use timers, event counters, states, etc. Basically you can program these using a set of conditions that allow to capture extremely elusive bugs / events. At some point deep memory just runs out.

So the real logic analyzer are Tektronix and HP/Agilent ? For your information an USB logic analyzer can offer much more recording memory and it is quite questionable in most of the cases if timers, event counters, states … are need it at all. But in contrast from Tektronix and HP/Agilent probably those functions can be added.
You have to quantify that... The TLA7AA4 module has 32Mpts per channel. 128Mpts in quarter channel mode. And don't forget timestamped recording which I doubt USB LAs have. I have used the timestamped recording feature on my TLA715 + TLA7AA4 module to capture several frames worth of data from a TFT screen using a 500MHz sampling rate / 2ns time resolution. On top of that the TLA7AA4 has a short memory which is sampled using a sample rate of 8GHz (125ps timing resolution).

Another very usefull feature is to have something similar to segmented recording like you find on oscilloscopes. When a trigger condition is met, the TLA700 series can capture a chunk of samples and then wait for the next trigger. Again, this allows for spanning timeframes that you'll never be able to achieve using a logic analyser that can only do a single shot.

Bottom line: the USB logic analysers are nice for doing protocol decoding and light logic analysis tasks but they are absolutely not a replacement for a real logic analyser. Besides that, real logic analysers can be bought from Ebay for peanuts.

Let's emphasise that with an example...

Consder a system with a 100MHz clock, an address bus, a data bus, and an address valid signal. Every 1ms data is read, and you are only interested in reads from address in the range 1234 to 5678. You want to capture (up to) 10000 values read on the rising edge of the clock provided address valid is asserted and provided the address range is right.

A decent LA will only capture <=10000 values during the 10s window. A low-end LA capture all the irrelevant clock transitions (i.e.2e9 !). It could probably post process those gigasamples to only show all data reads. You would probably have to write your own filter to see only addresses in the range.

That is one very simple example of what a decent LA can do.

Then consider only being interested in those values that occur after the sequence of signal X being asserted followed by signal Y being asserted for more than 1.5ms.

Good luck doing that triggering with a low-end LA!

General point: a good LA allows you to focus on the useful information, by filtering out the crap from the data.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline suspensionTopic starter

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #10 on: January 07, 2023, 04:10:50 am »
Very useful info. I am biasing more towards the used hp/agilent/tek options.
I see TLA715 is mentioned a lot in here as well in other threads. Any particular reason? Any other options that can be recommended?
 

Offline Thomas

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #11 on: January 07, 2023, 05:31:57 am »
Some USB LA's have advanced triggering. I have the DigiView DV-518:
https://tech-tools.com/trigger-cfg.html



Don't know how it compares to the old boat anchors, but it sure is more capable than the usual Saleae toys.

Anyway, if I had the space I would probably go with a boat anchor too.
« Last Edit: January 07, 2023, 05:50:22 am by Thomas »
 
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Offline mtk

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #12 on: January 07, 2023, 07:19:39 am »
Some of the PicoScope models also have Advanced Triggers capabilities, including: Advanced edge trigger, Window trigger, Pulse width trigger, Interval trigger, Runt, Window pulse width trigger, Level dropout trigger, Window dropout trigger, Logic trigger, Digital trigger ... https://www.picotech.com/library/oscilloscopes/advanced-digital-triggers

Ultra-deep memory - PicoScope 6000E Series oscilloscopes have waveform capture memories of up to 4 gigasamples. https://www.picotech.com/library/oscilloscopes/deep-memory-high-performance-oscilloscopes

Regarding TEKTRONIX TLA715, the lowest price currently on eBay is US $699.99 + shipping from US $142.97 + import charges Est. $230.90, total US $1073.86. Doubtfully this amount can be called peanuts.
 
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Offline tggzzz

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #13 on: January 07, 2023, 09:42:28 am »
Very useful info. I am biasing more towards the used hp/agilent/tek options.
I see TLA715 is mentioned a lot in here as well in other threads. Any particular reason? Any other options that can be recommended?

A general point is that if you are interested in any serial interface's data for capture/trigger/filter operations, then a good tool might be a protocol analyser or printf() statements.

Apart from that, and without knowing the tools
  • the picoscope advanced triggers mentioned would seem to be useful up to a point, but not for sequences of events
  • the digiview triggers seem useful
  • presumably separate filters are also needed for capturing the data

If you can, use a tool's manual to understand how you can/can't use the tool's features for your expected use-cases.

If you go for an old machine, verify that it is fully functional and that it has all the necessary probe hardware. Just as with scopes, the probes are "merely bits of wire" that are become separated from the "big important box" :(
There are lies, damned lies, statistics - and ADC/DAC specs.
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Offline markone

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #14 on: January 07, 2023, 09:50:41 am »
Some USB LA's have advanced triggering. I have the DigiView DV-518:
https://tech-tools.com/trigger-cfg.html



Don't know how it compares to the old boat anchors, but it sure is more capable than the usual Saleae toys.

Anyway, if I had the space I would probably go with a boat anchor too.

I was not aware of this device, it looks quite capable for the price, does its windows application show captured data in real time fashion or you have to wait the end of recording phase ?
 

Offline Thomas

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #15 on: January 07, 2023, 11:29:39 am »
I was not aware of this device, it looks quite capable for the price, does its windows application show captured data in real time fashion or you have to wait the end of recording phase ?
It operates in the normal capture-process-display manner, with "Auto Run" or "Run Once" options on separate buttons. This can be fast or slow depending on sample speed, memory depth, number of signals and decoders, see under Performance section here:
https://tech-tools.com/digiview-sw.html

The software also has Search on captured data. I haven't used it, but it seems comprehensive:
https://tech-tools.com/searching.html

Overall the software is a bit unusual and takes some getting used to, but it's always responsive and stable. Never seen a crash.

BTW, I think this analyzer is a bit slow for the OP's applications.
And a bit expensive ::)
« Last Edit: January 07, 2023, 11:36:15 am by Thomas »
 

Offline mtk

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #16 on: January 07, 2023, 11:58:33 am »
Consder a system with a 100MHz clock, an address bus, a data bus, and an address valid signal. Every 1ms data is read, and you are only interested in reads from address in the range 1234 to 5678. You want to capture (up to) 10000 values read on the rising edge of the clock provided address valid is asserted and provided the address range is right.

DSLogic Analyzers have stage trigger supporting 16 stages of trigger flag. Each stage support logic operation (and/or) of 2 sets of trigger. Each set support edge/level trigger of all channels, invert and counter. There is also serial trigger - https://www.dreamsourcelab.com/doc/DSView_User_Guide.pdf. It does not look much convenient to set up, but it seems possible to filter the requested from you values ?
« Last Edit: January 07, 2023, 12:46:15 pm by mtk »
 

Offline nctnico

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #17 on: January 07, 2023, 12:49:54 pm »
Regarding TEKTRONIX TLA715, the lowest price currently on eBay is US $699.99 + shipping from US $142.97 + import charges Est. $230.90, total US $1073.86. Doubtfully this amount can be called peanuts.
Asking price isn't selling price on Ebay. You should be able to pick one up for $300 or so. Just make the seller an offer and you'll see pricing on logic analysers is very flexible. If not, then just wait a little bit for another one to pop up.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline nctnico

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #18 on: January 07, 2023, 12:55:50 pm »
Some USB LA's have advanced triggering. I have the DigiView DV-518:
https://tech-tools.com/trigger-cfg.html

This looks like a neat tool but what I'm missing from the specification are the input capacitance & impedance. And the capture buffer is quite small. 128Mbit in total (14Mbit per channel for the 9 bit version and 7Mbit/channel for the 18 bit version).
« Last Edit: January 07, 2023, 12:57:30 pm by nctnico »
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Offline markone

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #19 on: January 07, 2023, 01:12:48 pm »
DSLogic Analyzers have stage trigger supporting 16 stages of trigger flag. Each stage support logic operation (and/or) of 2 sets of trigger. Each set support edge/level trigger of all channels, invert and counter. There is also serial trigger - https://www.dreamsourcelab.com/doc/DSView_User_Guide.pdf. It does not look much convenient to set up, but it seems possible to filter the requested from you values ?

Serial trigger does not work at all with async serial and it's a huge pita to setup with I2C and SPI, stay away this thing if serial decoding is your job.
 

Offline mtk

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #20 on: January 07, 2023, 01:38:48 pm »
DSLogic Analyzers have stage trigger supporting 16 stages of trigger flag. Each stage support logic operation (and/or) of 2 sets of trigger. Each set support edge/level trigger of all channels, invert and counter. There is also serial trigger - https://www.dreamsourcelab.com/doc/DSView_User_Guide.pdf. It does not look much convenient to set up, but it seems possible to filter the requested from you values ?

Serial trigger does not work at all with async serial and it's a huge pita to setup with I2C and SPI, stay away this thing if serial decoding is your job.

Mine is in transit and can not test it right now. Have you tried submitting a support request via Github - https://github.com/DreamSourceLab/DSView/issues ?
 

Offline tggzzz

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #21 on: January 07, 2023, 02:12:10 pm »
DSLogic Analyzers have stage trigger supporting 16 stages of trigger flag. Each stage support logic operation (and/or) of 2 sets of trigger. Each set support edge/level trigger of all channels, invert and counter. There is also serial trigger - https://www.dreamsourcelab.com/doc/DSView_User_Guide.pdf. It does not look much convenient to set up, but it seems possible to filter the requested from you values ?

Serial trigger does not work at all with async serial and it's a huge pita to setup with I2C and SPI, stay away this thing if serial decoding is your job.

Arguably a protocol analyser can be more appropriate for such things.
There are lies, damned lies, statistics - and ADC/DAC specs.
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Offline tggzzz

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #22 on: January 07, 2023, 02:21:05 pm »
I was not aware of this device, it looks quite capable for the price, does its windows application show captured data in real time fashion or you have to wait the end of recording phase ?
It operates in the normal capture-process-display manner, with "Auto Run" or "Run Once" options on separate buttons. This can be fast or slow depending on sample speed, memory depth, number of signals and decoders, see under Performance section here:
https://tech-tools.com/digiview-sw.html

I think all tools will have that cycle to a greater or lesser extent, depending on what is meant by "process". The devil is in the details; manufacturers sometimes make it difficult to understand, and users don't always understand what they will actually need.

For some use-cases involving rare fast short-duration events, a lot of the "processing" has to be done before and during capture and display. If not then the rare event can be missed while captured buffers are being post-processed to see if something "interesting" occurred.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline Thomas

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #23 on: January 07, 2023, 08:03:07 pm »
This looks like a neat tool but what I'm missing from the specification are the input capacitance & impedance. And the capture buffer is quite small. 128Mbit in total (14Mbit per channel for the 9 bit version and 7Mbit/channel for the 18 bit version).

Yes, the capture buffer is quite small. But as with many USB logic analyzers, only transitions are stored (often referred to as compression). They claim 100M transitions can be captured in most cases. This can be tested here:
https://tech-tools.com/captures.html

But still - YMMV.
One should always consider data sheets and specs carefully.
Corner cases and unlucky circumstances are always lurking and waiting to ruin your day.

In this regard I think the boat anchors are a safer bet - I think they have fewer "hidden" limitations and surprises.
But then again - the DigiView is a lot smaller than the floppy drive of a boat anchor :)
 
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Offline nctnico

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Re: Which logic analyzer for FPGA work up to 300-400 Mhz
« Reply #24 on: January 07, 2023, 10:40:45 pm »
This looks like a neat tool but what I'm missing from the specification are the input capacitance & impedance. And the capture buffer is quite small. 128Mbit in total (14Mbit per channel for the 9 bit version and 7Mbit/channel for the 18 bit version).

Yes, the capture buffer is quite small. But as with many USB logic analyzers, only transitions are stored (often referred to as compression). They claim 100M transitions can be captured in most cases. This can be tested here:
https://tech-tools.com/captures.html

But still - YMMV.
One should always consider data sheets and specs carefully.
Corner cases and unlucky circumstances are always lurking and waiting to ruin your day.

In this regard I think the boat anchors are a safer bet - I think they have fewer "hidden" limitations and surprises.
But then again - the DigiView is a lot smaller than the floppy drive of a boat anchor :)
Yes and no. Typically I'd agree a boat anchor takes a lot of space and is a PITA to haul around the lab but the Tektronix TLA700 series is an exception. My TLA715 sits high up a shelve and I control it remotely from my PC. The probe cables are long enough to reach the desk below so basically I only have a few probe pods on my desk when using the logic analyser.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 


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