Updated power supply and the RTC card

[sje]

For only a few dollars, a single chip all-in-one microcontroller could be programmed to generate a 60 Hz sine wave and feed it to the S-100 RTC pin. Alternatively, the output could be a square wave and be sent straight into the RTC card's counter, bypassing the Schmitt trigger input.

[Geoff Harrison]

Originally Posted by sje

For only a few dollars, a single chip all-in-one microcontroller could be programmed to generate a 60 Hz sine wave and feed it to the S-100 RTC pin.

But the main advantage of choosing the 60Hz signal is how precise it is, at least over long time spans. A microcontroller generated signal would be no more accurate than the system clock.

If you need the precision of the line frequency, couldn't you hook up a small transformer and feed an unrectified 5v to bus pin 55 and let the VI/RTC card work like it would in an 8800b?

Geoff.

[sje]

I'd guess that the 60 Hz signal, or any other signal source, should have the same electrical ground as the circuit that's receiving it. There has to be a return path for the electron flow. Without this, it would be like trying to take a measurement with an oscilloscope probe without connecting its ground clip to the test circuit's ground.