Logic Analyzer

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bootloader9800

Joined Jan 12, 2021
27
Hi all, hope u r doing great!
What is is that a "Logic Analyzer" can do that an OScope cant do?
I have a Logic Analyzer from Amazon AND an OScope too. Seems like I really dont need the logic analyzer since I can analyze any logic square waves with the OScope.

Can some one tell me if the Logic Analyzer is redundant? Ty
 

MrChips

Joined Oct 2, 2009
23,519
An oscilloscope is able to display and sometimes analyze continuous waveforms, both analog and digital in nature.
More advanced oscilloscopes may allow you to capture 4 or more channels simultaneously and may also analyze digital waveforms of various protocols.

A logic analyzer is intended for multiple channels of digital signals, usually on very large number of channels, 16, 64 or more. A logic analyzer can be set to recognize parallel bit patterns. For example, suppose you are debugging a computer system and you need to capture what led up to a certain binary data being fetched from memory and to be able to capture the memory address and the computer instruction and code location all at the same time.
 

schmitt trigger

Joined Jul 12, 2010
438
Also logic analyzers allow you to decode the data in common protocols like I2C, SPI, USB, CANBus, and many more.

Higher end oscilloscopes may also have that capability, but it is usually an option you have to pay for.
 

ronsimpson

Joined Oct 7, 2019
1,227
I have several old logic analyzer. It can be hard to see a address bus with 16 lines. Most analyzers can combine groups of traces into a buss. I can have 16 lines report in HEX. 3F7A

So like a scope that captures on a falling edge, I can have the analyzer start at WR=0 & address =785A & CS=0 and the other inputs at "don't care".
 

tautech

Joined Oct 8, 2019
204
Also logic analyzers allow you to decode the data in common protocols like I2C, SPI, USB, CANBus, and many more.

Higher end oscilloscopes may also have that capability, but it is usually an option you have to pay for.
Decoding the common protocols is standard fare for many entry level DSO's today. USB is another thing due to its speed.
Even a cheap scope can display signal integrity whereas a LA is not designed for this.
 

andrewmm

Joined Feb 25, 2011
1,467
Logic analysers have there place, but as the OP highlighted, a lot of the jobs they used to do a re now taken up by decent scopes.

My thoughts ,

LA's came around when scopes were BIG, and were analog,
If you had a waveform that was many 10's of ms long, and you had a data transition or two on it of a few ns, then it was "impossible" to see on a scope,
you could trigger on the edge, and see one transition, but if you wanted to see when the next was and how wide that one was , you had real problems.

LA's solve that problem, by recording events and when they happened, so they could easily capture that above, but not tell you what voltage the transition was at, just it was above threshold.

The CPU's and buss came along, and the need to watch many lines at once, and view the data as "hex" became in valuable,
this just about came to an end with the i486, which was a real pain to wire up to a LA, could take a half day ,
after that, processor s started having better on chip debugging, ability to implement break points etc.

LAs still survive,
but like the spectrum analyser, which scopes and FFTs are replacing for lower frequencies, LAs are becoming more specialised ,

I don't know when I last used a LA, got to be 20 years now. ...
scope, every day ,
 
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