GAL,PAL,PLD, CPLD,FPGA

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GAL,PAL,PLD, CPLD,FPGA, (what else...?)

GAL : Generic Logic Array
PAL :  Programmable Array Logic
PLD : Programmable Logic Device
CPLD : Complex Programmable Logic Device
FPGA : Field Programmable Gate Array

Can someone explain with comparison what is the difference between all these
GAL,PAL,PLD, CPLD,FPGA, (what else...?)  logic units?

Can all these units can be programmable with VHDL ?




Re: GAL,PAL,PLD, CPLD,FPGA

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I thought this was: Gate Array Logic.

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That's a language. As long as someone has a tool to convert VHDL source
code to the device's expected "bit" file then yes.

--
- Mark ->
--

Re: GAL,PAL,PLD, CPLD,FPGA
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These are all PLDs. I'm not sure where the border is between SPLD (Simpled
PLDs) and CPLDs. PALs were some of the first PLDs. There were also PLAs
(Programmable Logic Arrays). These two were fuse programmable, you programmed
them once. GALs (as far as I know) are PALs that use some form of non-volatile
memory for the "fuse bits". I don't know if they use EEPROM or FLASH. At least
a company I do work for switched from PALs to GALs and it was nice not throwing
PALs away when we had to make a change.

I think of PALs and GALs are SPLDs; FPGAs as CPLDs.

But then, I'm a software guy.  :-)


Re: GAL,PAL,PLD, CPLD,FPGA

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When I see those terms (which is probably NOT how Marketing sees them)
I differentiate between SPLD and CPLD by the presence of an interconnect
matrix that is distinct from the sum of product terms matrix within a
logic block.

<waves hands furiously in air and commits a Gross Oversimplification>
An SPLD has goes-ins and goes-outs with a sum of product term matrix
connecting everything to everything. A CPLD is two or more SPLDs wired
together with an interconnect matrix that is mostly wires, not gates.

<continuing with hand waving>
An FPGA, on the other hand, distributes many more registers more or less
uniformly throughout the device, associating each register with a
relatively (to CPLDs) simpler selection of logic and, often, a small
amount of RAM.

Some designs can be realized in either a CPLD or an FPGA. However,
register-heavy or RAM-intensive designs (e.g. a microcontroller core)
are more appropriate to an FPGA. Address decoding, data latches, and
replacing handfuls of glue logic chips with a single device are more
appropriate to a CPLD.

--
Rich Webb   Norfolk, VA

Re: GAL,PAL,PLD, CPLD,FPGA

  <many gates> schrieb im Newsbeitrag
  > GAL,PAL,PLD, CPLD,FPGA, (what else...?)
  >
  > GAL : Generic Logic Array
  > PAL :  Programmable Array Logic
  > PLD : Programmable Logic Device
  > CPLD : Complex Programmable Logic Device
  > FPGA : Field Programmable Gate Array
  >
  > Can someone explain with comparison what is the difference between all
these
  > GAL,PAL,PLD, CPLD,FPGA, (what else...?)  logic units?
  >
  > Can all these units can be programmable with VHDL ?
  >
  >
  >

  Hello,
  As a long year digital expert I'll try to tell you the difference of all
these logic parts.
  First: the content of all of  them can be described by the language VHDL.
But this makes sense only with higher complexities, which big CPLDs and
FPGAs have.
  PLDs, PALs and GALs are the lowest complexity of logic arrays (f.e.
22V10 -> 10 Flip-Flops + AND/OR-Logic).
  CPLDs and FPGAs have more gates and Flip-Flops, where CPLDs have a more
fixed structure (predefined number of gates and FFs) , while FPGAs are
consisting sometimes of pure gates (ACTEL, Antifuse) and can be handled like
true gate arrays. FFs are built by gates then.
  For the high complexities VHDL is the right tool to handle big designs.
But you should keep in mind, that the later layout of the FPGA-chip depends
on the design (how many IO-ports, number of FFs, number of gates, number of
logic blocks etc.).
  The best way to learn about the digital designs is to use the partly free
tools and do a design by yourself.
  All suppliers have nice kitparts and offer design software .

  Have fun.

  Regards,
  Roland




Re: GAL,PAL,PLD, CPLD,FPGA
Dear Roland,

Thank you for your clear and easy to understand summary.
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free
Can you recomment a particular one to learn CPLD/FPGA and VHDL?


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VHDL.
like
depends
of
free



Re: GAL,PAL,PLD, CPLD,FPGA
<many gates> wrote in message
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I have a simple CPLD design on my webs site that may be used with the free
Xilinx Webpack software.

Leon
--
Leon Heller, G1HSM
http://www.geocities.com/leon_heller



Re: GAL,PAL,PLD, CPLD,FPGA
Thank you all..
Leon's page about CPLD,FPGA etc on
http://www.geocities.com/leon_heller/pld_starter.html contains a good
summary about these units.


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