[sdiy] Shift register sequence period

[Tim Stinchcombe]

Yep, that is the same circuit. Unfortunately just the usual hand-waving
explanation, and no reference to anything meatier.

I hope to respond to the other v. useful replies later tonight, after
work...

Tim

> There's actually a 4006-based noise generator in the 
> Transcendent 2000, 
> which I think is from 1978.
> The design itself is probably even older.
> 
> > and the earliest reference I've found to it so far is in a 
> 1990 book 
> > by Ray Marston, 'Integrated Circuit and Waveform Generator 
> Handbook'.