[Oberon] ALU 2015 and 2018

[Skulski, Wojciech]

Please find attached the RISC5Top.v with my comments which I added to get the intern started on the project. Last time when we hired an intern, he burned most of his time trying to understand the firmware which he was supposed to modify. A large part of his work was unproductive and now I understand why. This time I commented the top file (and other files as well, but less extensively) because we need to get the work done in the environment where qualified help is scarce. 

This file originally came from Magnus for Pepino, but otherwise it is the original 2013 top file with slight modifications for Spartan-6. We will need to extensively modify this project to interface it with our own signal processing firmware. We will also switch the memory from ASRAM to ZBT RAM. Extensive modifications will be plain impossible without understanding the architecture, which was not clear to me until I went over the code and wrote extensive comments. On that occasion I discovered some inconsistencies between the actual code and PO.Computer.pdf. 

Quite unfortunately, PO.Computer and other docs are not live. It is not quite possible to bring the PDF inline with the actual code. In this situation there is and there will be a disconnect between the code and the docs, unless a new set of docs is made for the actual code. The cheapest way of doing so is to put extensive comments in the code file itself. Such comments can be then updated together with the code, to keep the documentation consistent with the HDL. I did just that. This file will keep evolving when we make progress. 

I also wrote a PowerPoint presentation of the project and I can send it to anyone who is interested. It is reasonably short, only 60 slides or so. It too will receive facelifts and updates as the project is progressing. I hope to never repeat my mistake with the previous intern, whose time we burned on trying to understand the "as simple as possible" which in fact was not that simple.

Thank you for all the discussion.

W.
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