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RichTW
 Post subject: Shadow RAM control
PostPosted: Wed Jun 29, 2011 5:07 pm 
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Location: Málaga, Spain
Can anyone point me at some docs which cover how shadow RAM is controlled (at the hardware level) on both a B+ and a Master?

Basically I want to make sure it's completely disabled - neither paged in nor being displayed.

Will
Code:
LDA #0
STA &FE34

do the trick on both machines?

And on a regular BBC B, what will that do? (is it mapped to FE30 or just thrown away?)

Cheers!
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TomW
 Post subject: Re: Shadow RAM control
PostPosted: Wed Jun 29, 2011 6:22 pm 
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Yes and mirrors &FE30.
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RichTW
 Post subject: Re: Shadow RAM control
PostPosted: Wed Jun 29, 2011 9:10 pm 
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Sweet. Cheers Tom.
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jgharston
 Post subject: Re: Shadow RAM control
PostPosted: Mon Aug 08, 2011 3:23 am 
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RichTW wrote:
Basically I want to make sure it's completely disabled - neither paged in nor being displayed.
MODE (positive any number less than &80)
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RichTW
 Post subject: Re: Shadow RAM control
PostPosted: Mon Aug 08, 2011 7:04 am 
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Not if *SHADOW has been entered beforehand!

I wanted a direct hardware access solution (as I'm changing screen mode by direct poking so that the screen memory isn't cleared), and it seems that the solution which is compatible with everything is:

Code:
LDA #0
STA &FE34    ; disable shadow RAM
LDA &F4
STA &FE30    ; put FE30 back in case it was mirrored at FE34
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