FPGA in a Design

[Joshua K Drumeller]

In college I had the wonderful and thrilling experience to design with
FPGAs. I have learned a lot working with them. However, the FPGAs we were
using were in pre-designed boards and we just focused on programming them
with our assignments. My question is how do you incorporate an FPGA into a
permanent design of a circuit board?



The FPGAs we used would lose their programming when the power was
disconnected. So how would a circuit designer who wanted to use an FPGA in
their permanent design get around that? Are there FPGAs which you can only
once from a computer then solder it into a design? Or would you have to
design a circuit which would load an FPGA every time it is powered up in
your permanent design? Or something else?



I have been searching the internet for some time and most of the info I get
is about FPGA experimental design boards. IF any one can help me out here it
would be extremely appreciated.



Josh

 

[Mook Johnson]

Yes and Yes,

Actel make anti-fuse technology type FPGAs that you program and soler onto
the board. Forever that parts will remain as programmed.

Actels ProAsc is a flash based part that you can program (even setup for
incircuit programming for field upgrades) and change logic code when you
need to. Flash retains its memory when powered down.

Xilinx makes FPGA that load their programming from a seperate EEprom which
can be programmed and installed in a socket (8 pin dip) for reprogramming.

Altera is similar.

Lots of options.

 

[keith]

In college I had the wonderful and thrilling experience to design with
FPGAs. I have learned a lot working with them. However, the FPGAs we were
using were in pre-designed boards and we just focused on programming them
with our assignments. My question is how do you incorporate an FPGA into a
permanent design of a circuit board?

SRAM based FPGAs have a non-volitile source for their configuration data.
Typically this is an external serial ROM (the simplest, but most
expesive), or a microcontroller with some sort of PROM. One can also
program through a channel like a PCI bus.

There are other FPGA technologies that are non-volitile, though they're
several generations behind the technology curve. SRAM based FPGAs are
usually done on the same processes as microprocessors and have the
advantage of that performance.

The FPGAs we used would lose their programming when the power was
disconnected. So how would a circuit designer who wanted to use an FPGA
in their permanent design get around that?

As above, one puts a "boot PROM" in the circuit. There are many was to do
this.

Are there FPGAs which you can
only once from a computer then solder it into a design?

Yes, though they're not the fastest nor densest parts. They're alos a
PITA to use.

Or would you
have to design a circuit which would load an FPGA every time it is
powered up in your permanent design? Or something else?

Generally, yes. It's not a big deal though. The FPGA manufacturers build
several method of doing this into their devices. Depending on the design
constraints, one is less painfull than the others. ;-)

I have been searching the internet for some time and most of the info I
get is about FPGA experimental design boards. IF any one can help me out
here it would be extremely appreciated.

Google "logic jump station". Also look at the Xilinx and Altera sites.
There is a *ton* of information there.

 

[Ken Smith]

The FPGAs we used would lose their programming when the power was
disconnected. So how would a circuit designer who wanted to use an FPGA in
their permanent design get around that?

You can:

(A) Never disconnect the power. Using a lithium battery or the like, the
power can be left on. This is an insane thing to do unless you are
very worried about security.

(B) Use a FPGA that loads its data from a PROM that sits next to it.

(C) Use a FPGA that has a PROM co-packaged with it.

(D) Use one of the anti-fuse or the like ones.

(E) Load the code from a micro controller.