Recently, Gary Stringham has been running a series of interviews with providers of register design tools on his website. Register design tools seems to be an active area with several small companies (and some open-source tools) fighting for the market. I have written about Gary Stringham and register designs before, and it is an area that keeps fascinating me. There is something about the task of register design that keeps it separate from the main hardware design languages, tools, and flows.The different approaches taken by the tools supporting the register design task also illustrates some points about programming language standards, domain-specific languages, and exchange formats that I want to address.
In his most recent Embedded Bridge Newsletter, Gary Stringham describes a solution to a common read-modify-write race-condition hazard on device registers accessed by multiple software units in parallel. Some of the solutions are really neat!
I have seen the “write 1 clears” solution before in real hardware, but I was not aware of the other two variants. The idea of having a “write mask” in one half of a 32-bit word is really clever.
However, this got me thinking about what the fundamental issue here really is.
When I started out doing computer science “for real” way back, the emphasis and a lot of the fun was in the basics of algorithms, optimizing code, getting complex trees and sorts and hashes right an efficient. It was very much about computing defined as processor and memory (with maybe a bit of disk or printing or user interface accessed at a very high level, and providing the data for the interesting stuff). However, as time has gone on, I have come to feel that this is almost too clean, too easy to abstract… and gone back to where I started in my first home computer, programming close to the metal.