Dumb question: What are gate arrays for?

OK, not really a dumb question, though I probably should know more about these devices. (Used to work for a company that used lots of 'em in its products.)

So I'm seeking just the most basic explanation of what these devices (FPGAs, etc.) are used for. I understand that they're devices with lots of gates plus tons of little teeny tiny fuses that can be blown programmatically, creating customized sequential logic circuits. Don't know much more than that.

So what would you use a FPGA for, say, that you couldn't do, or that would be too difficult to do, with a microprocessor? Can someone give some simple examples? and an explanation of just what kinds of gates these critters contain would be helpful.

I'm not looking for an exhaustive explanation; I may never even use one of these things. I'm just curious. I guess I'm looking for an "executive summary"-type explanation.

hi CZ,
Look at these links for combinational logic applications.
Consider that you had designed a control circuit that used discrete IC logic gates and you wanted to produce the design for lowest cost say and make lots of them.
Using FPGA replacement for discrete logic IC's would become a viable option for cost and size reduction.

combinational logic - Google Search

FPGA's are a circuit board on a chip. They are true logic circuits not hampered by instruction cycle times or MIPS. They are fast, large amounts of I/O, and the design one can do with these devices is only limited by the imagination...

FPGAs operate in parallel so they are fast. Microprocessors are sequential and thus generally much slower.

FPGAs can have a large number of inputs and outputs so can handle a lot of different logic functions simultaneously.

FPGAs do logic. Microprocessors do programs (although they can be programmed to perform logic).

For prototyping dedicated logic circuits.

Faster then a programmable processor, slower then implementation of dedicated logic in final I.C.

RCinFLA said:

For prototyping dedicated logic circuits.

Faster then a programmable processor, slower then implementation of dedicated logic in final I.C.

Click to expand...

FPGA's find theirselves in many production systems. They have a distinct advantage in limited production runs and field-upgradable products.

OK, I'm getting the idea (esp. the parallel processing aspect--very cool). So can anyone give me a concrete example of what a FPGA might do, specifically? Or point me to such an example out there on the web? I'm still not real clear about what they actually do.

What kinds of gates are available in a FPGA? AND/OR/NAND/etc.? Shift registers? Counters? Latches? all that and more?

Best thing to do is start with looking at a CPLD. Check out this data sheet, it shows the architecture. Take note of the macrocell diagram.
https://www.electro-tech-online.com/custompdfs/2011/04/ds054.pdf

carbonzit said:

OK, I'm getting the idea (esp. the parallel processing aspect--very cool). So can anyone give me a concrete example of what a FPGA might do, specifically? Or point me to such an example out there on the web? I'm still not real clear about what they actually do.

What kinds of gates are available in a FPGA? AND/OR/NAND/etc.? Shift registers? Counters? Latches? all that and more?

Click to expand...

All of that and more. FPGA fabric is the ultimate in digital system synthesis flexabliity. If you can dream it, then you can build it. BTW, modern FPGA devices no longer uses fuse technology like the old-fashoned PLA's did. Instead, they are SRAM based. That allows the devices to be programmed and re-programmed an unlimited number of times, with no performance degradation.