I've been working on a number of schematics for CPLD projects that I use as a part of a larger project (specifically, a binary-to-bcd converter, and a model of the SN74HC165 Parallel-In Serial-Out shift register). I have figured out how to package a schematic into a larger schematic symbol for reuse in higher level projects. Now I'm interested in building up a library of my own custom models+symbols, something I can use on a number of different projects, track in source control, etc. I cannot find any guidance on a good way of doing this (i.e., which files I need to package up, how to put it in a library I can reference from other projects, and so forth).
I saw the wiki page for the 7400 VDHL library (http://dangerousprototypes.com/docs/740 ... ry_in_VHDL (http://dangerousprototypes.com/docs/7400_series_library_in_VHDL)), but I didn't see any kind of download link or explanation of where to get or how to use it. Can anyone point me to a guide or does anyone have any tips on how do to this?
Thanks,
Andrew
Hi Andrew,
I'm sorry, I don't know much about this. The schematics are binary files and versioning is only useful as a backup. The 7400 library was a flop, it should be removed b/c it's an abandoned project.
It looks like (for ISE Project Navigator 13.2, anyway), the schematic and symbol files are XML. It also looks like all you need is the schematic (.sch) and symbol (.sym) files to re-use a custom schematic in another project. Granted, XML is not terribly useful for viewing diffs meaningfully, but it's better than binary.
Granted, this isn't exactly the VHDL library that was abandoned. Can you provide any background info on why the project flopped? Just lack of interest? Technically infeasible? I found it very interesting and instructive re-implementing the 74HC165 and testing it out in the simulator, and could see having a mild interest in doing more, especially for simulation purposes. I found the Xilinx ISIM simulator, once I got the hang of it, worked pretty well, and I can see using it to model logic circuits even that are too big to fit in a CPLD, just to confirm my expectations about how they behave. Having a library of common logic ICs (instead of just the many varied, but low-level primitives available in the library) could be very useful.
I had not looked at the actual source files in a long time, thanks for the tip that they are XML now. Not the best, but still a huge improvement from binaries :)
The library flopped because the rentacoder I paid to do it disappeared after a few dozen parts :) I tried to find the files and attach them, but I don't think we even got those before he left.
Too bad.
I would be happy to starting putting together what I have into a library of sorts, maybe someone out there would take it and run with it as a tutorial.
Did you have a particular desire to see the library in VHDL for compatibility across a wider range of manufacturers and devices? I have no VHDL experience, and so the schematic entry is much easier for me to understand and test, esp. when working from a block diagram in a datasheet..
I prefer Verilog myself ;) I also started with schematics though. VHDL was just what we could hire someone to write.
Schematics can get unmanagable, and difficult to change. If you get to a point where you feel it's a drag on your work, give verilog a try. We have some simple LED blinking tutorials on the wiki:
http://dangerousprototypes.com/docs/CPL ... es#Verilog (http://dangerousprototypes.com/docs/CPLD:_Complex_programmable_logic_devices#Verilog)