FPGA Selection--

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I've attempting to select an FPGA for a new design.

The design will have 9 of the following:
       12 bit latches
       12 bit down counter
        1 bit output latch

So one measure of the size might be 25 registers * 9 = 225 registers.

The counting freq is 15 MHz.

The latches get loaded from an existing micro.  So I need a 12 input
pins for a data buss, 4 input pins for which register, a clock pin and
let's say 4 pins for control lines.
Along with the 9 output signals.

So another measure is 12+4+1+4+9 = 30 pins not counting power and

It would also be desirable to be packaged in a PLCC but TQFP in ok.

And the device should be reprogrammable using JTAG (add 4 more pins).

Voltage is not much of an issue.  However 5 V tolerant I/O would be

I've looked at Lattice and Altera and haven't found the perfect
solution.  I can  use larger than necessary Altera devices (ACEX1K)
but that seems to be the wrong direction.

Any suggestions/recommendations.


Re: FPGA Selection--
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  PLCC / 5V /15MHz / 225 registers is more trailing edge, so look at
Atmel's AT40K FPGA family (meets all features), or possibly a CPLD -
Lattices 4000 family have 5V tolerant I/O ?

Re: FPGA Selection--

Lattice's  ispMACH4000 is a great family and available in different
packages. However, George mentioned he want's to use a PQFP,and the
ispMACH4000 is not available in PQFP. Ttherefore I would like to
suggest a M4A3-256/128-10YC. This is the previous generation.
If price matters, and George can live with TQPF (which is actual a
smaller package) then he can chose the LC4256V-75T100C. This device
has 64 IOs.



On Thu, 22 Jul 2004 09:16:05 +1200, Jim Granville

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Re: FPGA Selection--
There is the XCR3256XL


This is a 256 macrocell part that operates at 3.3V.  It has
the required 225 flops (31 to spare), JTAG and is 5V tolerant
on the I/Os.  It is offered in both TQ and PLCC packages.
15 MHz would bea "piece of cake".  It's
overkill in the I/O , but more is
better than less.  
Of course, there is a 1.8V version, but it
does note tolerate 5V without extra circuitry on the outside.

Peter Alfke, Xilinx Applications
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Re: FPGA Selection--

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Check out the AT94K10 or AT94K05.
This gives you both the (AVR) micro and the FPGA.

Best Regards
Ulf at atmel dot com
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Re: FPGA Selection--

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You don't need an FPGA for something that simple, look at CPLDs.

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