Difference between revisions of "OSBYTE &70"

From BeebWiki
Jump to: navigation, search
m (1 revision)
(update)
Line 2: Line 2:
 
OSBYTE &70 (112) - Select Main/Shadow for VDU access
 
OSBYTE &70 (112) - Select Main/Shadow for VDU access
  
    Y=0 X=0 Use whatever the default for the current mode is
+
        X=0 Use whatever the default for the current mode is
 
         X=1 Use main memory
 
         X=1 Use main memory
 
         X=2 Use shadow memory
 
         X=2 Use shadow memory
Line 8: Line 8:
 
     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)
 +
 +
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.
  
 
==See Also==
 
==See Also==
 +
* [[OSBYTE &6C]] - Select Master shadow memory
 +
* [[OSBYTE &6F]] - Select BBC B shadow memory
 +
* [[OSBYTE &70]] - Select memory for Master VDU access
 +
* [[OSBYTE &71]] - Select memory for Master video display
 +
* [[OSBYTE &72]] - Select future use of shadow memory
 +
* [[OSBYTE &73]] - Select shadow bank
 +
* [[OSBYTE &74]] - Check for Solidisk shadow memory
 +
* [[Paging in video memory]]
 
* http://mdfs.net/Docs/Comp/BBC/Osbyte00
 
* http://mdfs.net/Docs/Comp/BBC/Osbyte00
  
[[User:Jgharston|Jgharston]] 21:45, 26 May 2009 (UTC)
+
[[User:WikiSysop|WikiSysop]] ([[User talk:WikiSysop|talk]]) 13:33, 8 March 2015 (UTC)

Revision as of 14:33, 8 March 2015

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

       X=0 Use whatever the default for the current mode is
       X=1 Use main memory
       X=2 Use shadow memory
   (Risc OS 1.00)
   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.

See Also

WikiSysop (talk) 13:33, 8 March 2015 (UTC)