LeCroy MS-500-36 vs Agilent 16702B LA - Page 1
Forum section: electronics / testgear

author: w2hx
author_rank: Contributor
timestamp: April 02, 2020, 08:30:48 pm
content: Hi friends,I am trying to decide whether to update my LeCroy 610Zi to add an MS-500-36 logic analyzer option or acquire an Agilent 16702B with lots of channels etc. The Agilent is older, with somewhat older UI, huge and heavy but pretty cheap. Probably 25% of the cost of getting my 610Zi software license and MS-500-36.My question to the group is, which has more/better capability? I don’t really know whether the lecroy implementation of this LA feature is like a "low capability LA", used for casual LA usage. And whether for heavy lifting, one really needs a dedicated LA? Like the Agilent? Again, I don’t know, maybe this is not true. Maybe the lecroy can do everything that the 16702B can do? I just have no idea.I know the most common response to these kind of open questions is "well, what will you be using it for?" The answer is "whatever comes my way" but mostly older 8 or 16 bit CPUs and more modern microcontrollers. Serial trigger and decode is a must, etc. Things like instruction mnemonics decoding for certain CPUs would be extremely useful, etc.I think the decision I need to make is if the extra cost of adding LA capability to my 610Zi is worth a smaller, lighter, more modern LA with advanced capabilities. Or whether it is really only for casual use and the larger, older, cheaper Agilent would have much more capability and therefore worth saving a bunch of money.So ultimately, really looking for opinions or to hear from anyone who has direct experience using both.ThanksEugene

author: MarkL
author_rank: Unknown
timestamp: April 03, 2020, 08:24:33 pm
content: Sorry to say I don't fit your category of "direct experience using both", but I do have a 16702B and am reasonably well versed in its capabilities.The MS-500, if I'm reading LeCroy's documentation correctly, is a timing analyzer. It samples the digital inputs at a fixed interval (like almost all MSO logic analyzers). The 16702B has timing analysis too, but it can also operate as a state analyzer. The state analyzer only captures data on the transition of a clock input, and optionally when configurable conditions are met.Both would be suitable for looking at the timing relationships of a lot of digital input signals, but the 16702B would make better use of a given amount of analyzer memory since it's one location per interesting state event, and better at sophisticated triggering based on program flow. Many of the 16702B acquisition cards have a 16 sequence trigger state machine that controls capture and trigger and is programmed through the GUI.The 16702B was really designed for the era of exposed parallel buses, and doing debugging and code flow analysis while developing those systems. It has a lot of API hooks allowing you to roll your own tools if you wanted something like a custom opcode or protocol decode. It also has analog scope cards where you can display up to 8 channels along with the digital analysis. The scope card can come in handy, but unfortunately are very limited due to their capture buffer of only 32k points.If one of your requirements is serial decoding, the 16702B has rudimentary trigger and decode on some types of serial streams. The triggers are constructed via the GUI, and under the covers actually use the 16-level state machine.But I think you would be disappointed in the small breadth of protocols supported, and the clunkiness of the interface compared to more modern tools that are targeted for microcontrollers and their plethora of serial interfaces. I have never opted to use the serial capabilities of the 16702B and instead reach for a Saleae logic analyzer, which I'd highly recommend as a companion for any scope. Even one that's already an MSO.If you haven't already found it, you can read more about the 16702B here:http://literature.cdn.keysight.com/litweb/pdf/5968-9661E.pdfThere's a section in that document with an overview of the (limited) serial capabilities.All the option licenses, including serial analysis, are available for free and with the permission of HP/Agilent/Keysight, provided they are used only for non-commercial purposes. There are a lot of opcode decoders (in HPAK parlance "inverse assemblers") for older 8 and 16 bit processors, many posted to other threads in this blog.That link seems to be broken. Hopefully it will get fixed. Try this copy:http://www.libertytest.com/assetmanager/uploaded/pdf-2010823-94153-hp_16522a.pdf

author: nctnico
author_rank: Super Contributor
timestamp: April 03, 2020, 08:48:50 pm
content: If you are into logic analysers then look at the Tektronix TLA700 / TLA7000 series portables mainframe too. The advantage of the Tektronix logic analysers is that each sample has a 56 bit timestamp so in state-change-only recording you can a huge amount of memory depth. On the Agilent logic analysers you lose half the memory.It depends on your requirements whether an MSO or LA is better. LA usually offers extremely versatile triggering options which can be useful to find the most elusive problems (saved my bacon several times). An MSO can (typically) show signal realtime which is handy too. Although you have to be careful with Lecory's MSO option: some where kind of a add-on hack which never worked well. I don't know if this is the case for the 610Zi.

author: MarkL
author_rank: Unknown
timestamp: April 03, 2020, 09:40:26 pm
content: Quote from: nctnico on April 03, 2020, 08:48:50 pmTrue, but you can also choose to keep the memory depth and disable half the inputs on a card and use that slice of memory for the timestamps instead. User's choice at config time: less width or less memory for transitional (state-change-only) storage.An annoying choice, but it's the reason I always use the cards in pairs. You can then have 1.5 cards width (102 inputs) *and* get timestamps at the same time. Depending on the model card, timestamps can represent elapsed time of 17 seconds @ 4ns resolution (32 bits), or 32 days @ 2ns or 1.5ns resolution (?? bits).Tek and Agilent were definitely keen on specmanship for these units.