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Finished Parameterization & Added New Logic Cell

A project log for Open Source FPGA

An open source FPGA implementation.

Will LongWill Long 06/23/2016 at 01:583 Comments

Two big things: I finished parameterization of the homogenous logic cell assemblies, and I updated the logic cell design.

Parameterization means a few things. It's much easier to integrate a new logic cell into the routing fabric than it was before. The routing automatically adjusts itself to add more switches and wires to accommodate more inputs and outputs. The number of logic cells is also configurable; that means that arbitrary size and dimensions for the homogeneous array can be specified in.

The new logic block is much more capable than the original one. It is basically copied from the design shown on the Wikipedia page for FPGAs. There are four inputs and one output, plus a carry bit in and carry out. The four inputs feed into two 3-input lookup tables, which are selected between by the fourth input (allowing it them to be used a 4-input LUT). There is also a toggle-able full-adder and D-flipflop. Using the full-adder forces the LUTs to behave as two tables with three inputs.

At this point I want to experiment with routing using the MOSIS cell library and verifying the design.

Discussions

john wrote 06/28/2016 at 19:39 point

OK.  Chip silicon is well known, but costs so much it must target large groups of buyers somehow.  Those large groups already buy closed FPGAs and don't seem to care about open.  Finding some way to go forward without all-or-nothing large money campaigns is why I suggest printable electronics even though they are a little new, and some materials have a functional lifetime of just a year or two.

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john wrote 06/27/2016 at 00:07 point

Are you thinking of crowd funding a MOSIS run?  Have you thought about making large scale printed organic semiconductor FPGA?  The costs are much lower than FPGAs...and the performance also.  But think of how well PCbs are made today and making an FPGA implementation on some layers of a PCB, with the chips added on one side...  Could be a good niche market for some things that benefit from lots of parallel sensing and controlling where the fanout to the real world does not need micro size and for apps with low to medium signal speeds.  What if your FPGA cells could be made with organic semi and built on PCB layers?

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Will Long wrote 06/28/2016 at 19:03 point

Definitely planning on doing a MOSIS run. I'm hoping to use the
Hackaday Prize to help pay for it, but crowdfunding is also a good
idea. 
Regarding organic semiconductors, it's a neat idea but it's
beyond me right now. I'd be biting off a lot more than I can chew by
using an exotic technology.

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