[Coco] Clock rates

[Joe Grubbs]

Thanks Ed. I had forgotten the onboard crystal was 14.318. I'll decipher what I can from the 6883 datasheet... Might lead me to more nagging questions :P



--- Original Message ---

From: "Zippster" <zippster278 at gmail.com>
Sent: March 6, 2015 6:27 PM
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Subject: Re: [Coco] Clock rates

Joe,

The SAM chip (6883) is connected to a 14.318mhz crystal, and uses this to generate the video clock (3.579mhz),
and MPU clocks (separate clocks).  There is some information in the 6883 data sheet on synchronization between the 6847
MPU for RAM access.

- Ed


> On Mar 6, 2015, at 5:11 PM, Joe Grubbs  wrote:
>
> This is a question to the digital experts out there. I've taken electronics classes in school, focusing mostly on analog with a brief foray into simple logic circuits.
>
> It seems like the 6809, 6883, 6847, and 1372 were all meant to go together as a package, and were all meant to use a 3.579 crystal as the basis for the clock.
>
> I've looked at the datasheets and I can't tell if it's possible for the 6809 to run with a different clock while the 6847 and 1372 operate on the traditional 3.579 clock for proper display. Will the 6883 properly handle everything under those circumstances (keep memory refreshed, etc), or must everything be locked together as they are in the Color Computer?
>


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