OSBYTE &6C

From BeebWiki
Revision as of 21:27, 3 April 2015 by Jgharston (talk | contribs) (Added Integra-B info.)
Jump to: navigation, search

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

 On entry:
   X=0 Main memory appears from &3000 to &7FFF
   X=1 Shadow memory appears from &3000 to &7FFF
 On exit:
   X=previous state

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

Shadow RAM on the BBC B with the Integra-B system is also paged in with OSBYTE &6C. The Aries and Watford systems use OSBYTE &6F.

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

Jgharston (talk) 20:27, 3 April 2015 (UTC)