24k #13 -- get it on

6502, 8086, Z80, 8051, 6809, 68k, and so on. Early personal computing is full of inscrutable part numbers that remain memorable decades later. LC88FC2F0B? Not so much. LC88? No? Sanyo LC88?

Google will get you a data sheet for the LC88FC2FOB, a microcontroller from On Semi that features 24k RAM. The data sheet will tell you that it’s an example of the Xstromy 16 architecture (alternately Xstormy). But what’s that?

Google harder and you find that the LC88 was a Sanyo product family absorbed into On Semi together with the rest of Sanyo Semiconductor. You can also find a note that the LC88 is not compatible with the related LC87. Hmm. Roll the odometer a bit further back and we see the Sanyo LC86, an 8-bit microcontroller with 168 bytes of RAM. The LC85 is a Sanyo clock radio chip that looks too dumb to be an ancestor. Pull the thread further and you get to LC66 then the LC6500 family. By 1976, Sanyo was using 6502-series chips made by Rockwell in their line of calculators and …

Oops! As appealing as that story is, the LC6500 is not a Sanyo clone of the Rockwell clone of the 6502. It’s Sanyo’s own 4-bit microcontroller. I haven‘t figured exactly when it came out but I’m going to say that this is a product with big VHS slot-loading energy. Well, big low-power energy anyway. The LC6500 series microcontrollers and successors appear to have been used mostly in low-power interface and automation roles. Especially where that meant a little LCD display and an IR remote control.

If the 4-bit LC6500 family isn’t related to the MOS 6502, is it related to anything else? This is rabbit hole down which five hundred of the words of a post typically disappear but I can’t find any ancestor here. There are a lot of ways to build a small microprocessor. Sanyo‘s catalog reflects several such attempts. The LC57 series of Sanyo 4-bit controllers seems unrelated, marketed to makers of multifunction digital clocks. The LC5645N LCD watch controller doesn’t seem like a likely direct precursor to any of these processors. That watch chip probably has fewer transistors than my mechanical watch has moving parts.

Another low-tech way to dig into the provenance of these processors is to look at what the datasheet says about the development environment. The Sanyo datasheets I have surfed reference MS-DOS tools that you might run on IBM or Sanyo machines. Development environment, even tool chain, may be overstating what could have been a 50k DOS executable.

I guess this is where I say that I have no interest at all in Sanyo processors or in the LC88FC2FOB, our unlucky 13th member of the 24 x 24k for 2024 series.

That is, unless it’s so boring and opaque that maybe it is interesting after all.