Difference between revisions of "OSBYTE &6F"
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[[Category:OSBYTE]] | [[Category:OSBYTE]] | ||
− | OSBYTE &6F (111) - Read/Write Aries/Watford Shadow RAM Switch | + | ===OSBYTE &6F (111) - Read/Write Aries/Watford Shadow RAM Switch=== |
+ | This call is implemented by the Watford and Aries shadow memory systems for | ||
+ | the BBC B computer, and compatible systems. The B+, Integra-B and Master | ||
+ | series use different shadow selection calls. | ||
+ | On entry: | ||
X b7=0 no stack operation | X b7=0 no stack operation | ||
b7=1 pop state from stack (reading), push state on stack (writing) | b7=1 pop state from stack (reading), push state on stack (writing) | ||
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&C0 - Pop and select stacked RAM state | &C0 - Pop and select stacked RAM state | ||
&C1 - Pop and select stacked RAM state | &C1 - Pop and select stacked RAM state | ||
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==See Also== | ==See Also== | ||
− | * [[OSBYTE &6C]] - Select Master shadow memory | + | * [[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: | + | [[User:Jgharston|Jgharston]] ([[User talk:Jgharston|talk]]) 20:28, 3 April 2015 (UTC) |
Revision as of 23:51, 14 February 2016
OSBYTE &6F (111) - Read/Write Aries/Watford Shadow RAM Switch
This call is implemented by the Watford and Aries shadow memory systems for the BBC B computer, and compatible systems. The B+, Integra-B and Master series use different shadow selection calls.
On entry: X b7=0 no stack operation b7=1 pop state from stack (reading), push state on stack (writing) b6=0 write switch state b6=1 read switch state b0=0 select video RAM b0=1 select program RAM On exit, X contains the previous switch state: b0=0 video RAM b0=1 program RAM This gives the following entry and return values: X=&00 - Select video RAM &01 - Select program RAM &40 - Read current RAM state &41 - Read current RAM state &80 - Save current RAM state and select video RAM &81 - Save current RAM state and select program RAM &C0 - Pop and select stacked RAM state &C1 - Pop and select stacked RAM state
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 &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