# FPGAs - What are they, and what are they good for?

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#### Marks256

##### New Member
So i've been looking into FPGA (field programmable gate array) lately, and they look quite nice, but very intimidating... From what i have read, i understand them to be basically fully configurable processors. It seems that the HDL code specifies HOW the device will be used, then the program code tells it WHAT to do. Is this correct?

And what are FPGAs good for? I stumbled across this website (fpga4fun.com - Welcome) and they are using them just like microcontrollers! Is this true? are they a configurable microcontroller with memory and rom? So they can be used for just about anything a microcontroller can be used for?

#### BrownOut

##### Banned
First of all, FPGA's are NOT configurable microcontrollers, although many modern devices have processors built in. At the most basic level, they are substitutes for glue logic, or what we used to build digital logic with, 4000-series, 74-series IC's, etc. In other words, where you would previously buy a bunch of chips with logic, flip-flops, buffers... and then wire them together to create your system, now you simply program your logic design into one of these marvelous devices, and just wire it onto your board, and that's your project. Further, you can buy FPGA's with embedded devices such as processors, memory, DSP, etc.

The subject of FPGA could easily fill a thick book ( and it does ) Hope my ten cent explanation helps.

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#### Marks256

##### New Member
Yes that explanation helped a lot.

I guess i should have looked at that website i linked to in the OP... there is an explanation on what FPGAs are. I'll give that a read before i ask any more dumb questions. (this is the link fpga4fun.com - What are FPGAs?)

#### Hero999

##### Banned
Have you looked it up on Wikipedia first?

An FPGA is a huge array of uncommitted logic gates which can be connected up to form the desired system. They aren't MCUs but you can easily internally build an MCU out of them on the FPGA. FPGAs are potentially far more powerful than microcontrollers because they have much better parallel processing capability. Having a problem with a slow program on an MCU that uses lots of instructions? Easy modify the MCU core by adding your own fast instructions that perform several steps in one clock cycle.

#### Marks256

##### New Member
Yes i looked at the wikipedia page. I finally understand what they are now, and they look very attractive. I think i may buy a starter kit for them.

Thanks all

#### tcmtech

So whats the real cost to set up a basic system? I see starter kits going around $1200 and up! They looked great and very interesting even to a non micro controller guy like me but is there a cheap setup system I am not finding? #### tony ennis ##### New Member I thought I saw a combo Xylinx CPLD/FPGA development kit for like$150.

FPGAs are suitable for implementing CPUs. CPLDs are more of the 'pile of gates' chip.

#### Marks256

So whats the real cost to set up a basic system? I see starter kits going around $1200 and up! They looked great and very interesting even to a non micro controller guy like me but is there a cheap setup system I am not finding? Check out this website. Digilent Inc. - Digital Design Engineer's Source More specifically check out the Nexys-2. It is$129.99, but $99.99 if you are a student. The Basys System Board also looks very nice$79.99, $59.99 for students. #### andy257 ##### Member Check out this website. Digilent Inc. - Digital Design Engineer's Source More specifically check out the Nexys-2. It is$129.99, but $99.99 if you are a student. The Basys System Board also looks very nice$79.99, \$59.99 for students.
I second the above, i bought the Nexys 2 board which has a Spartan 3E included. Totally overkill for what i intended to use it for. If you just want to start up go for a CPLD it will be far cheaper and you will learn just the same language to configure the device.

Oh - if your in the UK dont forget to add your import tax onto that price :-(

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#### Marks256

##### New Member
andy257 said:
Oh - if your in the UK dont forget to add your import tax onto that price :-(
Just out of curiosity, what is the import tax at?

#### monkeybiter

##### Member
I bought an end of line Xilinx [great free tools] CPLD kit from DigiKey I think, approx 50USD. I haven't a lot of time, but have found it quite easy to get quick and encouraging results. I would encourage you to dip your toe, and don't forget voltage levels when adding anything on.

#### tony ennis

##### New Member
Just out of curiosity, what is the import tax at?
I believe the VAT is 15% currently, and 17.5% normally.

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