Difference between revisions of "OSBYTE &70"

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m (Corrected OSBYTE variable location.)
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OSBYTE &70 (112) - Select Main/Shadow for VDU access
 
OSBYTE &70 (112) - Select Main/Shadow for VDU access
  
         X=0 Use whatever the default for the current mode is
+
    On entry:
 +
         X=0 Use whatever memory the current screen MODE uses
 
         X=1 Use main memory
 
         X=1 Use main memory
 
         X=2 Use shadow memory
 
         X=2 Use shadow memory
     (Risc OS 1.00)
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     On exit:
 +
        X=preserved
 +
    RISC OS:
 
     The value of X can be greater than 2 as well, and instructs the VDU
 
     The value of X can be greater than 2 as well, and instructs the VDU
 
     drivers to use the bank at screenbase+(X*modesize)
 
     drivers to use the bank at screenbase+(X*modesize)
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of memory while the other is being displayed.
 
of memory while the other is being displayed.
  
==See Also==
+
The setting is stored in the [[OSBYTE &FA]] variable.
* [[OSBYTE &6C]] - Select Master shadow memory
+
 
 +
==See also==
 +
* [[OSBYTE &49]] - Check for Integra-B shadow memory
 +
* [[OSBYTE &6C]] - Select Master/Integra-B shadow memory
 
* [[OSBYTE &6F]] - Select BBC B shadow memory
 
* [[OSBYTE &6F]] - Select BBC B shadow memory
 
* [[OSBYTE &70]] - Select memory for Master VDU access
 
* [[OSBYTE &70]] - Select memory for Master VDU access
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* http://mdfs.net/Docs/Comp/BBC/Osbyte00
 
* http://mdfs.net/Docs/Comp/BBC/Osbyte00
  
[[User:WikiSysop|WikiSysop]] ([[User talk:WikiSysop|talk]]) 13:33, 8 March 2015 (UTC)
+
[[User:Jgharston|Jgharston]] ([[User talk:Jgharston|talk]]) 01:11, 4 April 2015 (UTC)

Revision as of 02:19, 4 April 2015

OSBYTE &70 (112) - Select Main/Shadow for VDU access

   On entry:
       X=0 Use whatever memory the current screen MODE uses
       X=1 Use main memory
       X=2 Use shadow memory
   On exit:
       X=preserved
   RISC OS:
   The value of X can be greater than 2 as well, and instructs the VDU
   drivers to use the bank at screenbase+(X*modesize)

This call specifies which bank of memory the Master VDU drivers access. Using this and OSBYTE &71 a program can use the VDU to write to one bank of memory while the other is being displayed.

The setting is stored in the OSBYTE &FA variable.

See also

Jgharston (talk) 01:11, 4 April 2015 (UTC)