Difference between revisions of "OSBYTE &6F"

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(Added ROMSTROBE information.)
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[[Category:OSBYTE]]
 
[[Category:OSBYTE]]
OSBYTE &6F (111) - Read/Write Aries/Watford Shadow RAM Switch
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===OSBYTE &6E (110) - Write to ROMSTROBE===
  
    On entry:
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  On entry:
     X b7=0 no stack operation
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     X= new ROMSTROBE value
      b7=1 pop state from stack (reading), push state on stack (writing)
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  On exit:
      b6=0 write switch state
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     X= old ROMSTROBE value
      b6=1 read switch state
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      b0=0 select video RAM
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      b0=1 select program RAM
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    On exit, X contains the previous switch state:
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      b0=0 video RAM
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      b0=1 program RAM
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    This gives the following entry and return values:
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     X=&00 - Select video RAM
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      &01 - Select program RAM
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      &40 - Read current RAM state
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      &41 - Read current RAM state
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      &80 - Save current RAM state and select video RAM
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      &81 - Save current RAM state and select program RAM
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      &C0 - Pop and select stacked RAM state
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      &C1 - Pop and select stacked RAM state
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This call is implemented by the Watford and Aries shadow memory systems for
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The value passed in X is written to the ROMSTROBE port and the RAM copy, the
the BBC B computer, and compatible systems. The B+, Integra-B and Master
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old value of the RAM copy is returned. Implemented in the Electron Plus 1
series use different shadow selection calls.
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Support ROM. The ROMSTROBE port is at &FC73 on the Electron, and writes
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the byte of data while the ROMSTROBE line is activated on the cartridge
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slot.
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===OSBYTE &6E (110) - Early Watford DFS double-step control===
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Do not use - use *OPT40,n and *OPT80,n.<ref>''The Micro User'', August 1986, p.22.</ref>
  
 
==See Also==
 
==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
 
* http://mdfs.net/Docs/Comp/BBC/Osbyte00
  
[[User:Jgharston|Jgharston]] ([[User talk:Jgharston|talk]]) 20:28, 3 April 2015 (UTC)
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==References==
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<references />
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[[User:Jgharston|Jgharston]] 21:17, 26 May 2009 (UTC)

Revision as of 02:15, 14 January 2016

Contents

OSBYTE &6E (110) - Write to ROMSTROBE

 On entry:
   X= new ROMSTROBE value
 On exit:
   X= old ROMSTROBE value

The value passed in X is written to the ROMSTROBE port and the RAM copy, the old value of the RAM copy is returned. Implemented in the Electron Plus 1 Support ROM. The ROMSTROBE port is at &FC73 on the Electron, and writes the byte of data while the ROMSTROBE line is activated on the cartridge slot.


OSBYTE &6E (110) - Early Watford DFS double-step control

Do not use - use *OPT40,n and *OPT80,n.[1]

See Also

References

  1. The Micro User, August 1986, p.22.

Jgharston 21:17, 26 May 2009 (UTC)