SPROM for Spartan II

Worth looking at Platform Flash for size and price. Usually much cheaper than the older programming prom families.

If this is a new board then go the further stage and use Spartan-3 your design. You will have to protect the Spartan-3 against 5V and may need 5V level shift if you have 5V CMOS level logic but you will benefit still from cost savings etc. Spartan-2E will need the similar protection and level shifting so no advantage over Spartan-3 in this respect. Spartan-2E is generally dearer than Spartan-3.

It is also worth getting in contact with the Xilinx University Program if you are a student or within an academic department. They can help out various aspects FPGA selection etc.

John Adair Enterpoint Ltd. - Home of Broaddown2. The Ultimate Spartan3 Development Board.

Spartan

very

Spartan

XC2S30

IIE,

Be sure your design fits in the part you are choosing, first. Note that the XCS30 has a lot more CLB's than the XC2S30. The "30" K-gate number in the Spartan II comes partially from the block RAM you didn't have in the older part.

Look at PlatformFlash (1 Mbit minimum size at about $3 in quantity). If you go this way the Spartan IIE looks better unless you have 5V interfacing issues. Using a cheaper PROM loses its advantage if you need to add a CPLD to interface it. Also the PlatformFlash is easy to program in system using iMPACT.

Xilinx

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so

for

any

Before the PlatformFlash came along I used Atmel Dataflash parts for large bitstreams (16Mbits +), but in that case I had a tiny micro to help with the job. For something like a 2-wire serial EEPROM (24C512) you could add a PIC micro for under $1 and get the job done if you're not too worried about the total configuration time.

up

Spartan-3 only comes in even bigger sizes than Spartan-IIe! The SPROM kills the cost advantage. I'm loading my XCS30 FPGA from a 256 KBit SPROM. I have to go to a 512 KBit SPROM to use the XC2S30, but the smallest Spartan-IIe part is the XC2S50xxE, which bumps you up to 1 MegaBit.

Nope, not a university project. This email is my "day job", the project in question is for my own business. Anyway, the design fits just fine in the XCS30 chip, so I don't want to be forced into a larger array needing more config bits.

Thanks,

Jon

Yikes! I didn't realize this! Thanks for bringing it to my attention!

Does this emulate a serial PROM? Or, do I need address counters and shift registers to make a serial stream? (I guess if it is byte-wide, I could use the parallel configure mode.)

Everything external is 5V. But, I can buy a lot of level translators for the $15+ difference between 5V Spartan and Spartan-II.

Clearly. And, another part to program, too! But, if I can do the interface with only 2 74HC-type chips, that is not too bad.

Well, as I said, I think I've figured out a way to use slave serial mode to do a slightly slower config with only 2 74HC chips. Nothing to program but the PROM, and it can go as fast as the PROM can spit it out (400 KHz). But, I'll look into this PlatformFlash.

Thanks,

Jon

But are you using a dedicated SPROM? The Spartan-3E is designed explicitly to gluelessly take advantage of cheap SPI memories allowing a very low configuration cost even if it takes more configuration bits. Lower than the other solutions you appear to be considering. If you were making 500k units in the end of 2006, your price for the XC3S100E plus an SPI PROM would be about $2.50.

kills

This particular product has no CPU on the board, and no other FPGA. So, the PROM is dedicated just for this one purpose. As it turns out, the Spartan-II XC2S30 is not big enough (A big thanks to Gabor for pointing this out - it never even ocurred to me that a Spartan-II 30K gates had no relation to a 5 V Spartan 30 K gates.) So, the smallest XC2S50E is about the right size.

This product will NEVER, ever see thousands of units made, no less half a million! And, if I do the conversion, I'd need to be testing in a couple of weeks. By 2006, it might be obsolete.

Thanks for the info, though.

Jon