John Payson wrote:
>
> I don't know who makes those particular MCU's since there's no
> packaging on them other than the blob, but expect that they're
>  mask-prog'd 4-bit'ters.


I don't know which processor is in the Tamagotchi-brand products
but I have seen quite a few products of that type. One of the
more interesting processors that is often used in watch style
products is the Sanyo LC5800 series. It is a RISC processor with
a 15 bit instruction path and 4 bit data path. It has a
programmable gate array that is generally used to directly
multiplex an LCD display up to 120 segments or so.

The processor executed at 4096 instructions / second with a
32Khz clock and at full speed required something like 2.3uA. In
sleep mode essentially no power.

Walter Banks