Difference between revisions of "OSBYTE &70"

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m (Corrected OSBYTE variable location.)
m (See Also)
 
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[[Category:OSBYTE]]
 
[[Category:OSBYTE]]
OSBYTE &70 (112) - Select Main/Shadow for VDU access
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{{PageTitle|OSBYTE &70 (112) - Select Main/Shadow for VDU access}}
  
 
     On entry:
 
     On entry:
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* [[OSBYTE &49]] - Check for Integra-B shadow memory
 
* [[OSBYTE &49]] - Check for Integra-B shadow memory
 
* [[OSBYTE &6C]] - Select Master/Integra-B shadow memory
 
* [[OSBYTE &6C]] - Select Master/Integra-B shadow memory
* [[OSBYTE &6F]] - Select BBC B shadow memory
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* [[OSBYTE &6F]] - Select Aries/Watford shadow memory
 
* [[OSBYTE &70]] - Select memory for Master VDU access
 
* [[OSBYTE &70]] - Select memory for Master VDU access
 
* [[OSBYTE &71]] - Select memory for Master video display
 
* [[OSBYTE &71]] - Select memory for Master video display
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* http://mdfs.net/Docs/Comp/BBC/Osbyte00
 
* http://mdfs.net/Docs/Comp/BBC/Osbyte00
  
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[[User:Jgharston|Jgharston]] ([[User talk:Jgharston|talk]]) 01:11, 4 April 2015 (UTC)
 
[[User:Jgharston|Jgharston]] ([[User talk:Jgharston|talk]]) 01:11, 4 April 2015 (UTC)

Latest revision as of 19:27, 22 January 2021

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)