Difference between revisions of "OSBYTE &70"

From BeebWiki
Jump to: navigation, search
m (moved OSBYTE 70 to OSBYTE &70)
 
m (See Also)
 
(8 intermediate revisions by 2 users not shown)
Line 1: Line 1:
 
[[Category:OSBYTE]]
 
[[Category:OSBYTE]]
OSBYTE &70 (112) - Select Main/Shadow for VDU access
+
{{PageTitle|OSBYTE &70 (112) - Select Main/Shadow for VDU access}}
  
     Y=0 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)
+
     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)
  
==See Also==
+
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==
 +
* [[OSBYTE &49]] - Check for Integra-B shadow memory
 +
* [[OSBYTE &6C]] - Select Master/Integra-B shadow memory
 +
* [[OSBYTE &6F]] - Select Aries/Watford 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: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)