Advice on PC Based Logic Analyzer

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Hi

I'm considering to purchase a pc based logic analyzer. After a bit of
shopping around I narrowed down my options to either the Logicport
from Intronix or the Annie-USB from Janatek, maybe even their Logic-16
as well.

Before I make the final decision, is there anyone of you that owns any
of these instruments?
The obvious reason for the logicport is the fact that it costs only U
$389 for 32 channels and 500Mhz sampling rate. I have however read
this little faq article on janatek's website on how to
evaluate(compare) between various logic analyzers and I'm having
doubts of buying a logicport. The Annie-USB although a tad more
expensive seems to be a really good quality instrument. Any of you
having thoughts on this.

Luckily the need is not pressing so I have a couple of days.

Re: Advice on PC Based Logic Analyzer
In article

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8 channels is too low for a logic analyzer
16 is a minimum
34 is far enought

you must count $500 for a complete logic port with some grabbers...!

I never heard of this annie-usb before...
but saw a lot of people around here happy with their logicport

so...make your choice !

--
Jean-Yves.

Re: Advice on PC Based Logic Analyzer
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What I like about the Annie-USB is that it comes complete with SMD
grabber clips that optionally would cost some extra money.
If you have the time go to www.janatek.com/annie-usb_main.htm. It
retails just below $500..My only concern thou is that it sports only 8-
channels. However they have a nice little article on their website
about evaluating logic analyzers and I must say that I agree with this
article in that I will rather buy 8 'good channels' with sufficient
buffer depth than 32 channels and anyway not be able to use them all.

The faq article is at: http://www.janatek.com/faq_buying_logic_analyzer.html =
#6

I've talked to some people and most of them said that I should opt for
sufficient buffer depth. What is the feedback of those happy okes
using logicport?

Re: Advice on PC Based Logic Analyzer

snipped-for-privacy@k13g2000hse.googlegroups.com...
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(snip)

I fully agree with Jean-Yves, 8 channels is definitively not enough for a
logic analyzer. Put it this way : If you need only 8 channels then very
probably a decent 4-channels scope will be enough, and you will use such
scope far more often than your logic analyzer. However if you have a REAL
problem that actually needs a logic analyzer then you will need at leat
20-30 channels. Just thinking at the tasks for which we have switched on our
TLA704 in the past 2 or 3 years we always used more than 8 channels. Even
for the last use (debugging of a GPIB interface) we needed 8 channels for
data plus 8 channels of control lines.
Cheers,
Robert
www.alciom.com



Re: Advice on PC Based Logic Analyzer
In article

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the logicport has a compression algorythm so that he can record days of
datas. it only records when the data changes.
the annie usb record also when the data dont change which is a waste of
buffer...
and definitely 8 channels is not enought

the logicport with 34 grabbers (and channels)  is around $500

the sufficient buffer depth is to compare with old logic analyzers that
had only some ko of memory and that are unusable today.
the logicport has enought.

--
Jean-Yves.

Re: Advice on PC Based Logic Analyzer
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That is true. It only records when data changes, But when your data
never changes why do you need a logic analyzer, and when your data
actually changes even at a moderatly freqency your little buffer would
fill up in no time.
Come on, if data compression was the epiphany solution, why would any
developing company at all offer you a deep sampling buffer.
Data compression is much cheaper to develop and manufactured.  Quote
article in Evaluation Engineering.
    "Lossless signal compression is included in this product because
its basic memory depth is 2,048 S/channel. To conserve memory, the
LA1034 only records data
     transitions. Lossless data compression relies on redundancy
within the data, which can be encoded to reduce storage requirements.
The amount of compression
     possible depends on the nature of the data. For example, the
LA1034 datasheet quotes a 233:1 maximum compression ratio or a factor
of greater than eight
     billion. This degree of compression is possible for a signal
starting with a single logic 1 followed by eight billion zeros. If
your signals typically consist of a few fast
     pulses with lots of dead time, compression can be very useful.
However, for very active signals with a large number of transitions,
the effective compression ratio
     will be small.
The reason Logicport offers data compression rather than a larger
sampling buffer is that they only use the little onboard memory
available in the single FPGA in their instrument.  (Quote article in
Evaluation Engineering)
       "The LA1034's logic and memory are entirely contained within a
single FPGA," commented Harrison Young III, company CEO. "This keeps
the speed up and the
       cost down compared with products having external memory
interfaces. The LA1034's efficient lossless compression algorithm
allows its buffer depth to be greatly
       extended with no loss in signal integrity."

Makes sense to me. Larger buffer makes even more sense




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Re: Advice on PC Based Logic Analyzer
On Tue, 15 Apr 2008 02:15:21 -0700 (PDT), logicgeek


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Eight are useful, 16 are better, and 32 (or more!) are occasionally
necessary. Like many things in life: "It depends."

The traditional need for 32 channels would be a 16-bit address bus,
8-bit data bus (or 8 A + 8 D + 8 A/D shared), plus a handful of
control lines. That enables one to trace a program's flow of
instruction and data fetches, jumps, etc. Typically one would trigger
on a specific instruction-fetch address and then examine the following
behavior. This kind of analyzer often came, or could be provided, with
the ability to interpret and display the assembler equivalents for the
captured data.

In the microcontroller world, however, generally the address and data
busses are contained within the processor core, so the analyzer is
relegated to watching the general-purpose I/O lines and the ports used
by peripherals. Much of the time, eight is indeed enough. But, if one
is managing operations on a chip with multiple 8-bit ports and a
handful of serial peripherals, one runs out of probes pretty quickly.

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Consider that a 1 Mbit buffer will be filled by a 10 Msps clock in
only 100 msec. If everything being examined by the analyzer is in the
same time scale, that may not be a problem but that 1 Mbit could turn
out to be far too short to look at fast events that are separated in
time.

A smaller buffer that incorporates transitional sampling does a great
job in capturing narrow but widely separated events. I usually sample
at 100 MHz and can easily look at related events separated by hundreds
of msecs (or longer).

There are times (no pun intended...) when there's a "lot going on" and
simply triggering on the easy target, e.g., first rising edge, would
fill the buffer before the event of interest. In that case, all that's
needed is to delay the trigger based on an edge count or time.

--
Rich Webb     Norfolk, VA

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