4 ms·

Seems like two large similar rectangular logic areas.... maybe one is state machine and one is display? Or maybe one is clock/date and one is UI?

• kens 4y ago
  I think it's one blob of standard-cell logic on the left with power routing through the middle. I don't think there is any visible partitioning into functionality in this logic. The large amount of analog circuitry in the right half is a bit of a puzzle. It looks like some large capacitors, maybe a charge pump for something?
  • addaon 4y ago
    This is outside my wheelhouse, but I assumed that the large capacitor area was a (trimmable) capacitor bank that could be put in parallel with the load capacitor on the (external) quartz oscillator, allowing calibration to counter some unit-to-unit variant in crystal frequency.
    • kens 4y ago
      That's a possibility, but I don't see any laser-trimming marks on the big capacitor. Another option would be selecting capacitors with fuses, but I don't see any fuses or capacitors with powers-of-two sizing. With the complexity of the circuitry in the right hand side, I think there are a bunch of analog things going on.
      • makomk 4y ago
        The calibration for quartz crystal variance in these watches is done much, much later in the manufacturing process using solder bridges on the PCB - people have reverse engineered it. I think there are watch oscillator chips out there with one-time programmable calibration (particularly for analog watches) though.