Glorified Plumbing

I was just browsing for fun this morning and found SYSTEM MANAGEMENT I2C, I3C AND SPI SELECTOR GUIDE, rev 7, by NXP. I’m glad to see this document has adopted updated naming for the SPI interface, but it’s not the same update everyone else followed. We can see that the bus components are a single controller and multiple targets. NXP updated the I2C spec (UM10204) in rev 7 to use controller and target, so it’s natural they would follow suit with SPI.

I know for a brief period OSHWA was proposing a similar convention, except using the term peripheral instead of target. There was a bit of a SNAFU, and it turns out that their acronym spelt out a rude word in a European language (I think it was Polish). OSHWA now uses PICO/POCI, but CIPO/COPI is used to name signals in the world of Arduino. OSHWA had an apology for the brief use of the offensive C-word, but I don’t see that on the page anymore.

I remember updating our internal documentation after the proposed change and before the correction. A fellow engineer reviewed my documentation a couple of weeks after I authored it, and they pointed out that I’d missed that memo. The changes came very swiftly in response to a general plea for inclusive or non-exclusive language in our industry. I wish I still had access to the page I wrote for that company. I had found pretty much every variant of SPI bus and serial shifter interface notation and documented our preferred forms.

Of course, in the world of dual, quad, and oct-SPI, we see terms like SDIO for serial data input-output, as the lines are now bi-directional in the wide bus modes. Devices that rely on a shift register as the interface sometimes use D/Q notation as used for flip-flops. Other devices have SDI/SDO paring, where a controller SDO would connect to the peripheral SDI, like a UART, you cross over in the middle. Unlike the I2C specification, which has a single owner, SPI has evolved from the original Motorola interface without a governing body.

I love language, and I love technology, but the ever-shifting vocabulary can be tricky to keep up with.