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Xilinx fpgas...

I've been looking at the Spartan 3an's mostly, because of the built-in config flash, but I've yet to settle on them as the preferred chip for my project. As it turns out, another chip I'm wanting to use is bga, and since it's unavoidable I've been looking for the same in the fpga. It would be really nice if there was a bga chip at or around 10-12mm in size... but I can't seem to find any such. Only the larger gate count fpga's are bga package, and most of those seem to come in at around 20mm in size... which means the board I'm working on would be wider than the dip chip that it's replacing. Something I'm willing to live with, but certainly more challenging because the chip is in several machines that each have their own board layout. I might have 2 inches of space below the chip on one machine, but can't even have a quarter inch worth of overhang in that same place on another.

Now, I do realize that an especially small package chip means that I won't be able to have a high gate count or as many io pins, but I don't believe my project even needs that.

So, does anyone have any suggestions? I'm not married to Xilinx, an Altera or Lattice chip that made things easier here would really rock.

Slight topic change: What do you guys think of this board for a learner's first fpga?

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It's well within my price range, I could afford more, and I don't want to get something so weak it can't even teach me anything. Is 100 kgates enough to implement an 8bit cpu? Would I be able to implement an ethernet core or usb with it? Etc. Just want an opinion.

Thanks, John O.

Reply to
John Oyler
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John,

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($149)

Has the kinds of resources that you need to really learn something. This platform is used at many colleges and universities, and there is a lot more "stuff" on the web for this board, than for the tiny little one for $49.

The $49 is a good board for prototyping a small design (connect the IOs to your stuff, create the design in the FPGA, test it, etc.).

As for a really tiny package, have you looked at CPLD's? Why does it have to be a FPGA if you really don't need much IO, and so few logic elements?

Austin

Reply to
austin

Some of the Spartan-3 and Spartan-3E chips come in a 8x8 mm CSP package:

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(see last page)

/Mikhail

Reply to
MM

To be honest, I'm not sure how much logic this needs yet. I'm wanting to do a modest FPU, actually. Probably not even worried about IEEE-754 compliant, just enough to add a few muliplication/division/log instructions to an old 8 bit cpu. I want to put the fpga "in front of" the cpu, intercepting the instructions it reads... if it sees a JSR and then a particular address it will be suspended, and the fpu takes over.

Supposedly, the 6502 was only about 5000 transistors, that's what,

2500 gates maybe? It's the cpu I want to augment. But an fpu has to be more complex, right? So I really don't know what I need yet... I'm just guessing that even the biggest cpld isn't quite enough, but that the smallest fpga in any family, even in the more modest ones, will be.

And it's kinda moot... I just checked WDC's site, and it looks like the 6502 is available in qfp44 as the smallest, still wider than a

600mil dip. Argh.
Reply to
John Oyler

The Spartan-3 and Spartan-3E are both listed as coming in a 8mm by 8mm CP132 package. We use a Spartan-3E with a SPI ROM for configuration. The Spartan-3E understands how to configure itself from a SPI ROM, so there is no additional external components required for configuration. To program the SPI ROM, we use JTAG to download a configuration into the Spartan that has a JTAG to SPI ROM bridge in it, then download what we want in the SPI ROM over JTAG. We are using the XC3S100E with a PicoBlaze 8 bit processor in it, plus a MiniSD controller, and it has room to spare. Up to the XC3S500E is listed in the CP132 package, so you would have three FPGA sizes to choose from.

Regards,

John McCaskill Faster Technology

Reply to
John McCaskill

Links ;)

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4-ND
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In a Spartan3E 500 you can fit a complete microblaze system...

Reply to
PFC

John

Our Craignell modules use the small CP132 package giving a choice of XC3S100E, XC3S250E or XC3S500E on these. There are very similar to what you want to do. Some pictures here

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There is a derivative of these boards coming shortly called Drigmorn1 that I am hoping will be the cheapest development board in the market and maybe the smallest as well.

John Adair Enterpoint Ltd.

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Reply to
John Adair

Why were you looking at the non-volatile chips of Xlinx? Only because of the on chip flash - or is it because you want to replace an older assp?

If so, and you are not restricted to 'Xilinx only' than you can have a look at Lattice XP, XP2 and MachXO. All these are non-volatile - have on board config flash and available in small 8x8 csBGA packages. The latter being the smallest LUT count.

Hope this helps,

Luc

Reply to
lb.edc

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