VHDL code for 16-32 bit counter for quadrature encoder signals (A-B)

Thank you Jamie.

"jamie" <jamie@noway.com> wrote in message 
news:6UC%c.17219$lP4.1220919@news20.bellglobal.com...
> Patrick Harold wrote:
>> Dear George,
>>
>> I would like to thank you for your understanding.
>> Unfortunatelly I'm not student. (I'm too old to be a student.. When  I 
>> was student, I was working with tubes (not even with transistors) ).
>> It is not so easy in my age to keep track with the all this new 
>> technologies. I'm trying my best to follow the technology. I recently 
>> started to study the VHDL. I'm almost on the "page one" of the VHDL study 
>> and want to learn by implementing simple little projects.
>> Thank you once again for your understanding.
>> Regards.
>
>
> Sorry Patrick, I'm use to students trying to do there homework online...
>
> Search amazon (and also google) for VHDL resourses.  I'd suggest you make 
> small devices and work up (make an invertor, make a flip-flop). Doing it 
> that way you will get use to the language and then you can focus on what 
> you really want to build.
>
>
> Regards,
>
> Jamie 

On Wed, 8 Sep 2004 20:48:14 +1000, <Patrick Harold> wrote:

>Unfortunatelly I'm not student. (I'm too old to be a student.. When  I was 
>student, I was working with tubes (not even with transistors) ).
>It is not so easy in my age to keep track with the all this new 
>technologies. I'm trying my best to follow the technology. I recently 
>started to study the VHDL. I'm almost on the "page one" of the VHDL study 
>and want to learn by implementing simple little projects.

I first learned on tube designs, as well.  Transistors were the 'new fangled'
thing for me, later on.  My first impressions, back when I was first reading
about transistors, were that tubes were quite superior, as transistors required
quite a bit more feedback to remain faithful to their inputs over a range.  Oh,
well.  Long time ago.

I don't have a lot of books on VHDL, but one that really helped me when I knew
nothing at all was a book by a British guy who moved to Alabama some years back
called, "HDL Chip Design."  It provides a nice introduction that assumes very
little by way of understanding and gives you a little history.  Elsewhere in the
book you will see both VHDL and Verilog examples of the same designs and he
covers a great many of the basics.  ASICs and FPGAs are discussed, with their
attendant differences in emphasis when designing, but not so much that you get
overwhelmed.  Examples are given to show you how changes in an approach can
yield improvements.  He discusses RTL and gate level optimizations in a way that
a newbie can easily fathom, I believe.  In short, regardless of possible errors
in the book today, it made a very easy path for me to get my first VHDL designs
up and running on a real FPGA board.  I went from not even knowing a single
keyword of VHDL to my first properly functioning 4-bit adder and 7-segment digit
display driver circuit in less than a week.  And the code wasn't borrowed or
stolen, I'd written it from scratch by myself.

Which books might speak better to you, I don't know.  But that one got me
started and gave me enough of the basics that I could then start reading the
VHDL others have written with some understanding and also begin to understand
other FPGA issues the book didn't cover, like floorplanning.  (obviously, I
don't care about ASICs as I'm unlikely to be designing any unless I come into
some cash I don't otherwise need.)

Jon

"Patrick Harold" wrote:
> 
> I would like to thank you for your understanding.
> Unfortunatelly I'm not student. (I'm too old to be a student..
> When  I was student, I was working with tubes (not even with
> transistors) ). It is not so easy in my age to keep track with
> the all this new technologies. I'm trying my best to follow the
> the "page one" of the VHDL study technology. I recently started
> to study the VHDL. I'm almost on and want to learn by
> implementing simple little projects. Thank you once again for
> your understanding.

Tubes are not all that different from transistors, especially
MOSFETs.  They are considerably bulkier, require much higher
voltages, need heaters, and dissipate much more power.  However
they are all 'gain blocks'.

However you should learn to post correctly.  Your answer belongs
AFTER (or intermixed with) the material to which you reply, AFTER
snipping out portions irrelevant to your answer.  This is known as
bottom-posting, and is always acceptable.  What you are doing is
called top-posting, which makes articles virtually unreadable and
allows them to grow indefinitely, like a cancer.

-- 
"I'm a war president.  I make decisions here in the Oval Office
 in foreign policy matters with war on my mind." -         Bush.
"If I knew then what I know today, I would still have invaded
 Iraq. It was the right decision" -       G.W. Bush, 2004-08-02

In article <413db1b1$0$19870$afc38c87@news.optusnet.com.au>, <Patrick 
Harold> says...
> I'm new to VHDL and I want to learn as with examples.
> I want to build a 16,24 or 32 bit counter for quadrature encoder signals (ie 
> A,B signals).
> Can someone help me how to create following functionality in VHDL ?
> 
<snip>

First of all split up your design into modules with a more 
specialized task.
I would suggest :
- A module for doing the conversion of the input signals 
  A,B,IDX into up and down counting pulses for the next 
  stage.
- a up-down counter 32/16
- the output stage for parallel output
- a parallel/serial converter and its output stage

This may be sufficient for learning purposes.
In practice, if you really want a working 
design you have to spend some thoughts about the
following :
- what happens when you are reading out during 
  a counting pulse from the encoder
- what happens if the encoder signals are 
  noisy and changing to fast or counting 
  continuosly up and down
- metastability

Last of all I would add a clock signal and make it 
a synchronous design.

Best regards   
-- 
Klaus Falser
Durst Phototechnik AG
kfalser@IHATESPAMdurst.it

Patrick Harold wrote:

>>>I would like to thank you for your understanding.
>>>Unfortunatelly I'm not student. (I'm too old to be a student.. When  I 
>>>was student, I was working with tubes (not even with transistors) ).
>>>It is not so easy in my age to keep track with the all this new 
>>>technologies. I'm trying my best to follow the technology. I recently 
>>>started to study the VHDL. I'm almost on the "page one" of the VHDL study 
>>>and want to learn by implementing simple little projects.

So did you download the Opencores example?:

<http://www.opencores.org/projects.cgi/web/quadraturecount/overview>

Paul Burke