[Coco] 6809 / General CPU question

[John Kent]

I'm sorry, I forgot to remove the SPAM notification in the subject heading.
My internet security software is a bit over zealous.
Why it should put "SPAM" in the subject header I have no idea.

John.

On 20/02/2011 5:49 PM, John Kent wrote:
> I suspect the vector is read into a temporary internal register then 
> transferred to the program counter as the program counter is used to 
> fetch the vector or at least it can be. The program counter would have 
> to be pre-initialized with all 1's in the high address bits and a 
> interrupt vector offset in address bits A3 to A1 on reset. I don't 
> know if that is how Motorola did it. I was a bit concerned about 
> patents, but I think they have all expired, so I don't think I'm 
> violating anyone's patent. I'm certainly not making any money out of it.
>
> John.
>
>
> On 20/02/2011 10:46 AM, Mike Rowen wrote:
>> Thanks everyone for your responses. Ok, so whenever the CPU powers on 
>> or experiences a RESET inturrupt, the CPU will read the contents of 
>> FFFE & FFFF and load it into the program counter register. It then 
>> fetches instructions from that location. Presumably this would be a 
>> location in ROM.
>>
>> How does an address get into FFFE & FFFF when the system is 
>> initialized? Is this through hardware? Are these RAM locations?
>>
>

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