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PostPosted: Sun Feb 12, 2017 2:08 pm 
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Joined: Thu Aug 16, 2012 7:55 pm
Posts: 27
This might be a stupid question-- but I am trying to write an 65816 emulator and at the moment I have a few doubts on this: should the direct page register be modified when operating in any sort of direct page addressing mode? Say for instance we have:

Code:
AND ($10, X)


The direct page register is something arbitrary like $01 right now... When after forming the indirect address, should the direct page register be modified to be the offset after the operation? Or does it stay the same?

Thanks!


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PostPosted: Sun Feb 12, 2017 2:14 pm 
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Joined: Sun Apr 13, 2008 11:12 am
Posts: 6028
Location: Seattle
The only instructions that change the D register are TAD=TCD and PLD. Anything else is equivalent to a temporary copy.


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PostPosted: Sun Feb 12, 2017 2:32 pm 
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Joined: Thu Aug 16, 2012 7:55 pm
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Thank you sir!!! :D


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