[Coco] 6x09 read and write strobes.

[jdaggett at gate.net]

On 19 Dec 2011 at 18:20, John Kent wrote:

> The 6809 was NMOS. I'm not familiar enough with the NMOS technology to 
> know how the internal clock phases worked. The 6800 had the requirement 
> that phase 1 and phase 2 of the input E clock not over lap and they had 
> special clock chips, the 6871 and 6875 (?) to do it.

The clock scheme is setup to move charge through the IC at varying times. A FET can act as 
a switch. Thus the clocks could gate charge movement or hold charge to act as a register. 
They did what they could do in IC development at that time. CMOS was still rather slow. 
PMOS was a current hog and awkward to interface to. NMOS with Depletion Loads offered 
the fastest and less power than bipolar.

james