[Coco] Javascript 6809 emulator

[Darren A]

On Sun, Mar 9, 2014 at 2:41 PM, Harry Hurst wrote:

>
> I just remembered something I wanted to ask about. In this TypeScript 6809
> emulator the author sets the S register to $BFFF on a reset, as well as on
> a cold start. I haven't tried to look it up yet, so I don't know, but I
> thought it would go to all zeros. It doesn't seem to be a big deal since
> the stack isn't used until it has been specifically be set to $9F00, but I
> thought I ask a quick question in here. What are the initial values placed
> in the registers of the 6809 at start up? I'm thinking all zeros. Does
> anybody think, or know, otherwise?



I believe the only registers that have a known state following Reset are:

CC = x1x1xxxx  (I and F are set)
DP = 0
PC = [FFFE:FFFF]

Everything else should be considered undefined.

Darren