AVR-Chat

Regarding logic analyzers I can offer the following from my own experiences
over the years below. FYI I also have an ANT-16 recently purchased.

Some things I have used an analyzer for..

1. Verify that timing signals to I/O chips meet the manufacturers
requirements including what is called "I/O delay"
where there is a rest period required between successive access to the same
part. When this becomes a problem, we use the jmp $+2 trick that flushes out
the instruction queue and gives a delay for Intel type CPU chips. Also
adjusting wait states in cpu chips that offer programmable wait states for
memory blocks and I/O blocks.

2. Events that are infrequent and take too long. A perfect example is an IRQ
request that is pending for too long for a UART and thus a character is lost
forever.

3. When you have a spare I/O port of say 8-bits you can create a function to
toggle on and off different bits so that you can window how long you are
taking in various software functions. When you are having problems it helps
to know where time is being spent.

4. looking at I2C and SPI signals when you are trying to talk to an external
device and things are not working. You can quickly check clock rates and
observe changes to them. Of course you can use a scope for some of these
things.

These are a few things that come to mind.

Al Welch
-----Original Message-----
From: Jeffrey Close [mailto:close@cafenoir.com]
Sent: Tuesday, November 25, 2003 11:36 AM
To: Allan Lane; AVR-Chat@yahoogroups.com
Subject: Re: [AVR-Chat] Re: PICO PC Based Oscilloscopes (Model:
ADC200/100)




I have been able to develop lots of MCU-based stuff without using LAs
because I'mnot that comfortable using them.

Unfortunately, this has meant finding very creative and often circuitous
ways of debugging problems that would be much easier solved with a logic
analyzer.

I would welcome suggestions from this group for good tutorials or a way to
get started learning to use LAs effectively...

thanks in advance,

cheers,
jeffrey





Allan Lane <allan.lane@honeywell-tsi.com> wrote :
>
> I have an Ant8 myself, and am very happy with it.
> 500 MHz means your max sample rate is 2 nS.  This
> means your logic analyzer can tell you when things
> really happen, +- 2 nS.
>
> At 40 MHz, you get +- 25nS -- still pretty good.
>
> Sometimes, you want to insure you catch some
> very transient (ie short) pulses.  At 40 MHz,
> you'll ignore anything shorter than 25 nS.
>
> --- In AVR-Chat@yahoogroups.com,
> techy fellow <techyf@y...> wrote:
> > Hi Alex,
> >
> > Thanks alot for the info. As I am into MCUs, I need an equipment to
> help me to test my projects. I will be getting an AVR ICD or ICD2 for
> PIC. But when comes to testing of circuits, I think I need something
> more than just ICD.
> >
> > I thought of using a logic analyzer since it is meant for digital
> circuits. Actually, I am about to build one appeared in Elektor
> magazine Feb 2003 issue. Top speed is 40 Mhz. Pale in comparison to
> the one sold by Rocky Logic (500 Mhz). I thought since almost all
> MCUs is less than 32Mhz (even for ATMega 128), a 40Mhz model should
> do the job. Why do we need 500 Mhz ?
> >
> > cheers,
> > Davis
> >
> >
> > Alex Gibson <alxx@a...> wrote:
> > techy fellow wrote:
> >
> > >Hi Guys,
> > >
> > >Can someone pls let me know whether the aforementioned is a good
> equipment to
> > >invest ? Or I should go for a typical 2 channels Oscilloscopes ?
> > >
> > >Thanks in advance for your help.
> > >Davis
> > >
> > >
> > >
> >
> > What do you need ?
> >
> > What frquency range ?
> > What bandwidth ?
> >
> > What are you going to use it for ?
> >
> > I usually use micros and similar boards up to 100MHz
> > so ended up buying two second hand scopes and a usb  based logic
> analyser.
> >
> > The one I use most of the time a HP 54502A
> > dual channel 400MHz dso.
> >
> > One I use only when I need to debug something
> > higher than 200MHz  HP54501  1GHz quad channel scope.
> >
> > Logic analyser  great when debugging micros.
> > easy to use and easy to carry.
> > http://www.rockylogic.com/products/ant8.html
> > http://www.rockylogic.com/products/ant8spec.html
> > good for up to around 100MHz.
> > I use this a lot. Windows software only though.
> > Still waiting on them to release their api
> > so you can call it from your own software.
> >
> > What I find is it is usually easier to have equipment that doesn't
> need
> > a computer.
> > Hit the switch and it is up and running.
> > Can have hassles with usb based equipment especially if other
> devices
> > your using use
> > the same manufacturers device but with a different driver or
> different
> > driver version.
> >
> > Alex Gibson
> >
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