why use an FPGA when a CPLD will do ??

Hallo,

Simon Peacock schrieb:

> There is also the issue that FPGA's configuration data is stored in external
> FLASH where as CPLD's are programmed.
> It is actually quite easy to reprogram a FPGA on the fly and field update
> the external memory while the FPGA is still running.  No special hardware or
> algorithms are required.  Downloading a CPLD is usually done from a PC via a
> JTAG cable or via a External Chip Programmer

This is wrong. At least if you accept other fpga vendors beside Xilinx
*g*

OK.. I admit there are a few minor players who have flash based or fuse
based FPGA's.. but then they aren't by definition field Programmable are
they?
They are in fact very large CPLD's as a FPGA is a Field Programmable Gate
Array and Fuse devices aren't field programmable (or at least are only
one-shot) FLASH devices could be considered field programmable... but some
can't be used while a new program is getting uploaded.  So that excludes
them from what I would call Field Programmable.

Although some people might disagree.. I believe that A&X do hold the lions
share of the market so RAM based rocks for now... until nano-tube becomes
the fad.

Simon

"Thomas Stanka" <usenet_10@stanka-web.de> wrote in message
news:1141631210.694896.38720@u72g2000cwu.googlegroups.com...
> Hallo,
>
> Simon Peacock schrieb:
>
> > There is also the issue that FPGA's configuration data is stored in
external
> > FLASH where as CPLD's are programmed.
> > It is actually quite easy to reprogram a FPGA on the fly and field
update
> > the external memory while the FPGA is still running.  No special
hardware or
> > algorithms are required.  Downloading a CPLD is usually done from a PC
via a
> > JTAG cable or via a External Chip Programmer
>
> This is wrong. At least if you accept other fpga vendors beside Xilinx
> *g*
>

The temptation is great,

Austin

Simon Peacock wrote:

> but sarcasm is so much better than a pointy stick.
> 
> Simon
> 
> "austin" <austin@xilinx.com> wrote in message
> news:dude5h$ar25@xco-news.xilinx.com...
> 
>>Duane,
>>
>>Yes, I apologize for my sarcasm.
>>
>>I had just read the posting concerning newsgroups, and how to get the
>>best answers from them.  This post was a classic example of someone who
>>had not even had the foresight to do any research on their own.
>>
>>Given that everyone who posts here has access to google (or any other
>>search engine), it is generally annoying to see questions that could be
>>answered by three minutes of browsing and reading.
>>
>>Sarcasm is the weapon of the weak, and I should have been more civil,
>>
>>Austin
>>
>>Duane Clark wrote:
>>
>>
>>>Hendra wrote:
>>>
>>>
>>>>Austin Lesea wrote:
>>>>
>>>>
>>>>>Matt,
>>>>>
>>>>>If you use a a cpld, you need to post in comp.arch.cpld
>>>>>
>>>>>Austin
>>>>
>>>>
>>>>There is no comp.arch.cpld
>>>>
>>>
>>>I suspect he was being facetious, and just forgot the smiley ;)
>>>
> 
> 
> 

Simon Peacock wrote:
> OK.. I admit there are a few minor players who have flash based or fuse
> based FPGA's.. but then they aren't by definition field Programmable are
> they?

Certainly they are.  Devices that are not "field programmable" are "mask
programmable" at the time the chip is manufactured.  That's been standard
semiconductor industry terminology for more than thirty years.

The original field-programmable devices used NiCr fuses, which later
gave way to TiW fuses, floating gate EPROM and EEPROM cells, and now
flash memory and RAM-based parts.

Matt Clement wrote:

> What are the advantages and disadvantages of using a CPLD instead of using
> an FPGA for a design?

Are some CPLD's more compatible with low-cost PCB's using fewer layers,
than certain FPGA's?  (memories of the spartan3 on four layers thread,
where officially six was rated minimum)

Simon,

I admit that X&A are controlling the FPGA market, but stating that
Flash based FPGA's are de facto not field Programmable is a bit of a
strong statement.
Both Actel and Lattice have flash based FPGA's, and Lattice provides a
technique not seen from X&A before. They call it TFR or TransFR, but
it is actually a manner of reconfiguring the FPGA while the system
operates. I have not seen this from the big players.
Maybe you will agree that in the telecom's world of today where five
nines or six nines is the buzz word, both Altera and Xilinx are
struggling to find an answer...

A humble FPGA designer

Luc


On Mon, 6 Mar 2006 21:14:49 +1300, "Simon Peacock"
<simon$actrix.co.nz> wrote:

>OK.. I admit there are a few minor players who have flash based or fuse
>based FPGA's.. but then they aren't by definition field Programmable are
>they?
>They are in fact very large CPLD's as a FPGA is a Field Programmable Gate
>Array and Fuse devices aren't field programmable (or at least are only
>one-shot) FLASH devices could be considered field programmable... but some
>can't be used while a new program is getting uploaded.  So that excludes
>them from what I would call Field Programmable.
>
>Although some people might disagree.. I believe that A&X do hold the lions
>share of the market so RAM based rocks for now... until nano-tube becomes
>the fad.
>
>Simon
>
>"Thomas Stanka" <usenet_10@stanka-web.de> wrote in message
>news:1141631210.694896.38720@u72g2000cwu.googlegroups.com...
>> Hallo,
>>
>> Simon Peacock schrieb:
>>
>> > There is also the issue that FPGA's configuration data is stored in
>external
>> > FLASH where as CPLD's are programmed.
>> > It is actually quite easy to reprogram a FPGA on the fly and field
>update
>> > the external memory while the FPGA is still running.  No special
>hardware or
>> > algorithms are required.  Downloading a CPLD is usually done from a PC
>via a
>> > JTAG cable or via a External Chip Programmer
>>
>> This is wrong. At least if you accept other fpga vendors beside Xilinx
>> *g*
>>
>

Hi,

Simon Peacock schrieb:

> OK.. I admit there are a few minor players who have flash based or fuse
> based FPGA's.. but then they aren't by definition field Programmable are
> they?

Yes, for sure. Field programmable has nothing to do with
reconfiguration.

> They are in fact very large CPLD's as a FPGA is a Field Programmable Gate
> Array and Fuse devices aren't field programmable (or at least are only
> one-shot) FLASH devices could be considered field programmable... but some
> can't be used while a new program is getting uploaded.  So that excludes
> them from what I would call Field Programmable.

Ever tried to use a xilinx device while uploading them? If my memories
correct,  uloading with parallel port took over a minute for the first
Virtex.

Ok, my answer on your last posting was a bit short, because a similar
thread started in comp.lang.vhdl a few days ago :=). Sorry, should have
used a full answer.

Originaly you had CPLD with less registers and weak routing abilities
providing fast pathdelays against FPGAs with more registers and good
routing but slow path delays.

Nowadays you differ between CPLD and FPGA mostly by marketing. The big
CPLDs from Altera and Lattice are AFAIK FPGAs on a technological point
of view. It seems to me only marketing to call them CPLD (maybe some
customer are used to CPLDs and would never change to Fpga).

bye Thomas