Oops,

I didn't read the link you posted until just now, it seems mine predates the TI-5020 by a year and to my mind it is a much better designed device.

Brian

The first significant purchase of my young life was a Sinclair calculator. I blew something like 80 quid on it (which was a VAST sum of money in the 70's) and 3 weeks later they reduced the price to 25 pounds.

Those of a certain age will know that it was a deeply unreliable beast and I had to fix the on off switch with a dab of solder if I remember. Probably the most use was in clever stories which ended up spelling Shell Oil upside down…

Iain

Any sort of processor with registers in it is liable to wake up with them in a random state. The usual way of dealing with this is to apply a power on reset. Typically this involves holding a reset line low until there has been enough time for the power line to become stable, eg switches have finished bouncing and so on. A common way of doing this is for the reset pin to have a capacitor to ground and a suitable resistor to the power rail. Once the capacitor has charged enough the system comes out of reset in a known state. This sort of scheme is much harder to apply to a solar powered device, where the power may come up very slowly. So it becomes easier just to rely on the user to press reset.

John