74ls373 or 74ls374 to FPGA?

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Hi guys,
  I am developing a project that involves tens of 8 bit buffers. I am
designing it with regular TTL logic but maybe in the future I will use FPGA
if the project works. Well, I know developing with FPGA is better but I
just don't have the initial investment and I have a lot of experience with
TTLs.

I can design it either with 74ls373 or 74ls374. If I use 74ls374, they will
not share a common clock. I am wondering which design is easier to transfer
to FPGA or CPLDs. I have little experience with FPGAs. What I know is that
they like registers with common global clock. Please inform me... Thank
you.

vax3900

Re: 74ls373 or 74ls374 to FPGA?
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  Look at the 74VHC273 - that's a HC374 D register, with a Reset, or
there are serial ones like HC594/HC595 which can save pins.
  Both will port to CPLD reasonably easily.
-jg


Re: 74ls373 or 74ls374 to FPGA?
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I don't think the 373 would port well as it is a transparent latch. I would go
with the 374.

Re: 74ls373 or 74ls374 to FPGA?
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The initial investment is almost nil.  Build a Xilinx Parallel Cable III
(schematic available in PDF from their website -- it's just some buffers
on the end of a parallel cable) to do JTAG programming and then get a
XC9572 for about $10.

Download the Xilinx WebPack (free) and design what you need.  You can
use the schmatic capture tool to design with the very 74 series parts
you're talking about.  Heck, do this even if you don't do the hardware
part.

The hardest part is mounting the chips, which don't come in DIP packages.
A PLCC-DIP adapter is more than the other parts you'll need combined (times
two, even!) but people have successfully fly-wired them from sockets, and
PLCC is very easy to solder directly (sockets not so easy to route on a
homemade board, but definitely possible).

--
Ben Jackson
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Re: 74ls373 or 74ls374 to FPGA?
Thank you, Ben, Ppelectron and Jim. I decided to go ahead with 74ls374.

I bought XC95144 (0.5mm pins) from ebay and adapter card from
http://web-tronics.com/qf32100pi0pi.html . I also got the schematic of Jtag
cable http://toolbox.xilinx.com/docsan/2_1i/data/common/jtg/fig26.htm . I am
ready to order the solder paste from digikey (with components to build the
jtag cable) and will use the oven method
http://www.seattlerobotics.org/encoder/200006/oven_art.htm . But this is
reserved to the core state machine design as buffers eat too much
flip-flops.

Thank you all.
vax3900


Re: 74ls373 or 74ls374 to FPGA?
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I don't remember the pin counts on the packages, but the XC95288 might
come in the same PLCC84 you can get the XC95144 in.  Sort of like the
XC9536 vs 72, same pins (in some pkgs), more internal gates.

I find the shortage of flops kind of strange.  FPGAs have several orders
of magnitude more storage.

--
Ben Jackson
We've slightly trimmed the long signature. Click to see the full one.

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