Difference between revisions of "OSBYTE &6C"

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[[Category:OSBYTE]]
 
[[Category:OSBYTE]]
OSBYTE &6C (108) - Main/Shadow RAM Usage
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OSBYTE &6C (108) - Main/Shadow RAM access
  
 
     Y=0 X=0 Main memory appears from &3000 to &7FFF
 
     Y=0 X=0 Main memory appears from &3000 to &7FFF
 
         X=1 Shadow memory appears from &3000 to &7FFF
 
         X=1 Shadow memory appears from &3000 to &7FFF
    This has immediate effect and allows the user to make use of the 20k of
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    extra RAM for other purposes.
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This has immediate effect and allows the user to access the Master's 20K
 +
shadow RAM, for instance, to load or save it or manipulate it directly. The
 +
memory that is accessed by the VDU drives and displayed can set with
 +
[[OSBYTE &70]] and [[OSBYTE &71]].
 +
 
 +
On the BBC B+ the displayed memory is always the bank selected with MODE or
 +
[[OSBYTE &72]], and the user can only access the shadow memory by calling
 +
[[OSRDSC]].
  
 
==See Also==
 
==See Also==
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* [[OSBYTE &6C]] - Select Master shadow memory
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* [[OSBYTE &6F]] - Select BBC B shadow memory
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* [[OSBYTE &70]] - Select memory for Master VDU access
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* [[OSBYTE &71]] - Select memory for Master video display
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* [[OSBYTE &72]] - Select future use of shadow memory
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* [[OSBYTE &73]] - Select shadow bank
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* [[OSBYTE &74]] - Check for Solidisk shadow memory
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* [[Paging in video memory]]
 
* http://mdfs.net/Docs/Comp/BBC/Osbyte00
 
* http://mdfs.net/Docs/Comp/BBC/Osbyte00
  
[[User:Jgharston|Jgharston]] 21:15, 26 May 2009 (UTC)
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[[User:WikiSysop|WikiSysop]] ([[User talk:WikiSysop|talk]]) 13:30, 8 March 2015 (UTC)

Revision as of 14:30, 8 March 2015

OSBYTE &6C (108) - Main/Shadow RAM access

   Y=0 X=0 Main memory appears from &3000 to &7FFF
       X=1 Shadow memory appears from &3000 to &7FFF

This has immediate effect and allows the user to access the Master's 20K shadow RAM, for instance, to load or save it or manipulate it directly. The memory that is accessed by the VDU drives and displayed can set with OSBYTE &70 and OSBYTE &71.

On the BBC B+ the displayed memory is always the bank selected with MODE or OSBYTE &72, and the user can only access the shadow memory by calling OSRDSC.

See Also

WikiSysop (talk) 13:30, 8 March 2015 (UTC)