I upgraded Code Composer Studio recently (Mac Version: 6.1.3.00034) and ran into a feature I hadn’t noticed before.

I was modifying the GPIO reading code from a couple weeks ago and saw something strange:

What is that exclamation point in a triangle? That doesn’t look good. I hovered over it and CCS explained the warning:

The build output had the same warning message:

"../main.asm", WARNING! at line 35: [W5369] Silicon Errata CPU40: A jump instruction at the end of a section should be followed by a NOP.

“Silicon errata” is a technical way of saying “a bug in the chip hardware.” It turns out that making chips is difficult, and fixing hardware bugs is much harder than just pushing a patch over the internet. Unlike software bugs, chip bugs and any workarounds are usually well documented by their creators: you can find the full list of MSP430 chips bugs here. Here’s what the errata document says about the error we ran into, CPU40:

You don’t have to understand everything it says to see that TI provides a lot of detail about what causes the bug and how to workaround it.

I count 82 chip bugs in that document. That’s pretty typical of most chips I’ve worked with.

TI’s Code Composer Studio IDE is the first development environment that’s warned me about a bug that I was about to run into - good for TI! And they didn't just warn me about a bug, they also told me how to fix it - thanks!

I added a NOP instruction as the IDE suggested and the warning went away.

(The NOP instruction means “No OPeration” - it literally does nothing except takes up space in memory and use a little bit of execution time.)

The cover image is by Windell Oskey of Evil Mad Scientist, CC BY 2.0. He shows you how to make your own chip bugs here.

This post is part of a series. Check out the complete Embedded Software Engineering 101 series here.