[Coco] FPGA

[jdaggett at gate.net]

On 18 Feb 2009 at 14:51, N8WQ wrote:

> Folks,
> Occasionally I hear the term FPGA used in various discussions here on
> the list. Can anyone recommend any books, tutorials, or url's that can
> help me learn about this subject?
> 
> Alan Jones
> 


FPGA stands for Field Programable Gate Array.  Xilinx, Altera, Lattice are 
the major manufacturers of such devices.

Primarily they are comprised of LUTs( Look Up Tables), RAM, multiplexors 
and filip flops. With a 4 input LUT you can synthesize just about any 4 input 
logic imaginable. The LUT can also be a 16 bit ram, a shift register, a 
decode or encode logic. With the basic building blocks of a FPGA you can 
synthesize just about any digital logic thinkable. 

FPGAs are programmed with a language that is known as HDL, Hardware 
Description Language. There are two major flavors of HDL, VHDL and 
Verilog. VHDL is a programming language that is based on ADA and has 
some similar chracteristics to Pascal. Verilog kind of mimics C. 

All the manufacturers of FPGAs have free development tools for their own 
products. Also there are other vendors that make tools that are more 
generic and can be used on different FPGA vendors. The advantage of the 
tools is that one can use a programing language to describe the bahevior of 
the digital circuit, compile the program and simulate the logic before 
synthesizing it to actual part. 

The best way to start learning is to determine which language you want to 
learn first, VHDL or Verilog. Both have their maerits and drawbacks. Once 
decided on either VHSL or Verilog, there are many tutorials on the web. 
Search these and then download either Alterra's Quartus or Xilinx's 
Webpack ISE and install that. Then it is just learning how to code and 
synthesize and simulate the designs. You can do this all without ever 
having to buy any FPGA development boards. 

Eventually you will want to actully test your design in real product. That 
there is another issue. Which vendor? That becomes a matter of choice. 

hope this helps soem

james