FPGA vs CPLD

[praveen]

Hello,
What is the differences between FPGA and CPLD?

What basis on which i should select. whether to go for cpld or fpga?

waiting for reply
with regards
praveen

 

[Leon Heller]

"praveen" <praveenkumar1979@rediffmail.com> wrote in message
news:ff8a3afb.0407280557.36cb274f@posting.google.com...

Hello,
What is the differences between FPGA and CPLD?

What basis on which i should select. whether to go for cpld or fpga?

It's getting very blurred. Altera's new CPLD, the MAX II, is really an FPGA,
apparently.

Leon

 

[General Schvantzkoph]

On Wed, 28 Jul 2004 06:57:51 -0700, praveen wrote:

Hello,
What is the differences between FPGA and CPLD?

What basis on which i should select. whether to go for cpld or fpga?

waiting for reply
with regards
praveen

Is this a serious question? The internal architectures are very different,
go download the architecture documents from the Xilinx site. From an
application standpoint FPGAs are much much bigger than CPLDs. CPLDs are
used for very simple glue logic applications, they are cheap and
nonvolatile. FPGAs can implement very complex systems, but they are more
expensive on a per package basis although they are much cheaper on a per
gate basis. FPGAs require some support logic to initialize them, either a
serial prom or an interface to a CPU (frequently implemented with a CPLD).

 

[Rene Tschaggelar]

praveen wrote:

Hello,
What is the differences between FPGA and CPLD?

What basis on which i should select. whether to go for cpld or fpga?

The common understanding is that CPLDs are EEPOM or Flash based
and have to be programmed once. They have up to say 512 Flipflops.
FPGAs on the other hand are RAM based, meaning they have to be
programmed at every powerup. This usually happens with a small
external Flash, a CPU or whatever. The smallest FPFA is far bigger
than the biggest CPLD.

Hope that helps.

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

 

[Linnix]

praveenkumar1979@rediffmail.com (praveen) wrote in message news:<ff8a3afb.0407280557.36cb274f@posting.google.com>...

Hello,
What is the differences between FPGA and CPLD?

General logics vs. Simple reg/decoder
Expensive ($10 - $20) vs. Cheap ($1 - $2)
Big (> 100 pins) vs. Small (> 44 pins)

....

 

[Jim Granville]

praveen wrote:

Hello,
What is the differences between FPGA and CPLD?

What basis on which i should select. whether to go for cpld or fpga?

10 years ago, things were relatively simple :
FPGA's were pretty much all RAM/loader designs, with low power,
and granular logic.
CPLDs were were higher power, fast with wide-logic terms, and
limited in register count.

These days, there is much more overlap and bluring of the lines.

# Some FPGAs are FLASH (Lattice, Actel)
# Some CPLDs have granular logic ( MAX II )
# Some CPLDs have RAM/Loader built in ( MAX II, Coolrunner... )
# For lowest static power, modern CPLDs are << modern FPGA

The first point of selection would be the register count, then
the logic/RAM/DSP considerations.

You could, in some cases, design with both ( or use uC + FPGA )
to solve all the design problems.

-jg

 

[Matt North]

How about an FPGA which looks like a CPLD (in programming terms)
No boot prom or external logic, instead this has internal eeprom.

http://www.latticesemi.com/products/fpga/xpga/index.cfm

 

[Mario Trams]

praveen wrote:

Hello,
What is the differences between FPGA and CPLD?

What basis on which i should select. whether to go for cpld or fpga?

CPLDs are most often used for less datapath intensive timing-critical
designs (i.e. more control-path like stuff), while FPGAs are fine
for highly datapath intensive designs.

FPGAs are rather easily scalable. That is, they have a structure
comparable to US-like (i.e. "constructed") cities. You have a very
regular grid with buildings (i.e. logic blocks) as well as horizontal
and vertical streets (i.e. the connections). You can easily extend
the structure at the borders.

CPLDs have a completely different structure. Mostly, there is a
centralized connection structure and the logic elements are grouped
around it. Thus, the analogy is something like a farm. You can
recognize easily that such a design does not scale very well.
Because of that, the CPLDs have a rather small capacity when
compared to FPGAs. However, they have the big advantage of a
predictably fast interconnection. I.e. it does not matter where
the logic elements are positioned - the delay of the connections
between them is almost the same. This is not the case for FPGAs.
There, the farther the elements are away from each other, the
higher the delay.

Besides this difference, CPLDs have mostly much more powerful
logic elements than FPGAs. This also attributes to the use
of CPLDs especially for control paths.

Another difference that has been already cited by others is
typically the non-volatile nature of CPLDs and the volatile
nature of FPGAs.

Regards,
Mario

 

[Thomas Stanka]

me@linnix.info-for.us (Linnix) wrote:

praveenkumar1979@rediffmail.com (praveen) wrote in message news:<ff8a3afb.0407280557.36cb274f@posting.google.com>...
Hello,
What is the differences between FPGA and CPLD?

General logics vs. Simple reg/decoder
Expensive ($10 - $20) vs. Cheap ($1 - $2)
Big (> 100 pins) vs. Small (> 44 pins)

I use Fpgas in 84cqfp while I have just read, that Altera ships its
new MaxII CPLD in up to 324 pin BGA.
I think the first point ist the best way to differ between CPLD and
Fpga.

bye Thomas

 

[Thomas Stanka]

Rene Tschaggelar <none@none.net> wrote:

praveen wrote:
What is the differences between FPGA and CPLD?

The common understanding is that CPLDs are EEPOM or Flash based
and have to be programmed once. They have up to say 512 Flipflops.
FPGAs on the other hand are RAM based, meaning they have to be
programmed at every powerup. This usually happens with a small
external Flash, a CPU or whatever. The smallest FPFA is far bigger
than the biggest CPLD.

That's pretty wrong. Actel has flashbased Fpgas (and antifuse based).

The main difference is that CPLDs are mainly focused on
Input->(fast)Logic->Register->Output
while Fpgas are typically slower for CPLD tasks, but have more
configuration possibillities and support more complex logic
structures.
A typical CPLD design would have fast but simple operations while a
fpga has complex operations based on many internal registers.

bye Thomas

 

[Gabor Szakacs]

Another point blurring the line between FPGA and CPLD is
pin-to-pin speed. 10 years ago an FPGA was clearly not
suited to fast asynchronous designs. Modern FPGA's, while
not as fast as the fastest modern CPLD are often fast enough
for functions like address decoding and asynchronous memory
interface.

Also you will find both FPGA's and CPLD's with programmable
I/O standards (LVTTL, LVCMOS, SSTL, HSTL, LVDS...)

Price per gate is still less in FPGA, but the overall price
range now overlaps considerably.

Still:

if the design is static and fits in a CPLD, you're probably
going to get off cheaper with a CPLD.

if the design requires instant-on you're again probably better
off with a CPLD, although a few FPGA's have this feature.

if the design requires flexibility to download different
logic depending on the end use, you're generally better
off with FPGA due to both the SRAM-based infinite-reload
capability, and ease of fitting designs after the pinout
has been fixed.

Jim Granville <no.spam@designtools.co.nz> wrote in message news:<YfXNc.909$zS6.112816@news02.tsnz.net>...

praveen wrote:
Hello,
What is the differences between FPGA and CPLD?

What basis on which i should select. whether to go for cpld or fpga?

10 years ago, things were relatively simple :
FPGA's were pretty much all RAM/loader designs, with low power,
and granular logic.
CPLDs were were higher power, fast with wide-logic terms, and
limited in register count.

These days, there is much more overlap and bluring of the lines.

# Some FPGAs are FLASH (Lattice, Actel)
# Some CPLDs have granular logic ( MAX II )
# Some CPLDs have RAM/Loader built in ( MAX II, Coolrunner... )
# For lowest static power, modern CPLDs are << modern FPGA

The first point of selection would be the register count, then
the logic/RAM/DSP considerations.

You could, in some cases, design with both ( or use uC + FPGA )
to solve all the design problems.

-jg

 

[Rajeev]

Lets take an example and see what the concensus is:

Gate Count: 40K ASIC gates
Speed: 50 MHz
PinOut: 100 pins
Other: ???


One Configuration: Spartan-III would be a suitable fit with $20
price tag (scaling to $10 with volume) + $3 prom.

Altenatives from Altera? Actel (may be anti fuse?)

Could some one fill in...

-Rajeev

 

[Mario Trams]

Rajeev wrote:

Lets take an example and see what the concensus is:

Gate Count: 40K ASIC gates
Speed: 50 MHz
PinOut: 100 pins
Other: ???


One Configuration: Spartan-III would be a suitable fit with $20
price tag (scaling to $10 with volume) + $3 prom.

Altenatives from Altera? Actel (may be anti fuse?)

Could some one fill in...

Where is the relation with my posting?

Mario

 

[Rene Tschaggelar]

Thomas Stanka wrote:

Rene Tschaggelar <none@none.net> wrote:

praveen wrote:

What is the differences between FPGA and CPLD?

The common understanding is that CPLDs are EEPOM or Flash based
and have to be programmed once. They have up to say 512 Flipflops.
FPGAs on the other hand are RAM based, meaning they have to be
programmed at every powerup. This usually happens with a small
external Flash, a CPU or whatever. The smallest FPFA is far bigger
than the biggest CPLD.


That's pretty wrong. Actel has flashbased Fpgas (and antifuse based).

The main difference is that CPLDs are mainly focused on
Input->(fast)Logic->Register->Output
while Fpgas are typically slower for CPLD tasks, but have more
configuration possibillities and support more complex logic
structures.
A typical CPLD design would have fast but simple operations while a
fpga has complex operations based on many internal registers.

True, Flash FPGAs blurr the line. However according to the data
I have available some of your statements are also not
correct. The fastest CPLD I came across does in the order of
220 MHz, and has no internal multiplier. Whereas the FPGAs,
at least the more modern ones tend to have clock multipliers
and 220 MHz is not considered fast at all.

Rene

 

[Rajeev]

Mario Trams <Mario.Trams@informatik.tu-chemnitz.de> wrote in message news:<cedcm7$nn7$1@anderson.hrz.tu-chemnitz.de>...

Rajeev wrote:

Lets take an example and see what the concensus is:

Gate Count: 40K ASIC gates
Speed: 50 MHz
PinOut: 100 pins
Other: ???


One Configuration: Spartan-III would be a suitable fit with $20
price tag (scaling to $10 with volume) + $3 prom.

Altenatives from Altera? Actel (may be anti fuse?)

Could some one fill in...


Where is the relation with my posting?

Mario

Mario,

I was trying to being up an example so that we could see which techonlogy
from which vendor makes best sense. This happens to be a design I worked in
the past.

-Rajeev