Re: Hacking the Laser 128EX/2

[Rubywand <rubywand@swbell.net>]

Rubywand wrote:
>
 ....

>>
     Getting back to the oscillators, 3.6864MHz is an interesting frequency.
It seems to be interger divisable to obtain all of the major telecom baud
rates.

     This could explain the choice of "3.6MHz" (instead of 4MHz) as the uP
clock frequency. My guess is that the 3.6864MHz osc serves as both the uP
clock and the base for generating serial port baud rates.
<<


     Here's another possibility which, really, fits things better. Maybe the
3.6864MHz osc is entirely devoted to baud rate generation. The "3.6MHz" number
for the Laser's speed comes from 3.5795MHz. This, of course, is the color burst
frequency which comes from dividing down 14.318MHz.

     Since Laser needs to be Apple II compatible and it needs color burst,
using color burst for the uP clock cuts costs and also links/syncs the uP clock
to other important A2 frequencies. (And, if Laser ran at 3.6864MHz, it seems
like marketing would advertise speed at "3.7MHz" rather than "3.6MHz".)

     If the above is correct, you may be able to go to "7MHz" (7.16MHz) by
using the 7M signal for your system clock. Otherwise, it looks like messing
with the 3.6864MHz crystal will not help and you are pretty well locked into
your current speed.



Rubywand