Difference between revisions of "OSBYTE &B9"

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[[Category:OSBYTE]]
 
[[Category:OSBYTE]]
OSBYTE &B9 (185) - Read MOS copy of palette register
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OSBYTE &B9 (185) - Read/Write MOS copy of palette register/ROM polling semaphore
  
     (Electron OS)
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     On the BBC, B+ and Master, this contains the MOS's copy of the palette
     Read/Write ROM polling semaphore
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     register in the video ULA.
     This is the value adjusted by *FX22 and *FX23
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    On the Electron there is no video ULA, and this location contains the ROM
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    polling semaphore. When the semaphore is non-zero the 100Hz ROM service
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     call &15 is sent to ROMs. The semaphore is normally accessed with *FX23
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    to increment it and *FX24 to decrement it.
  
 
==See Also==
 
==See Also==
* http://mdfs.net/Docs/Comp/BBC/OsbyteA6
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* [[OSBYTE &16|OSBYTE &16]] - Increment ROM polling semaphore
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* [[OSBYTE &17|OSBYTE &17]] - Decrement ROM polling semaphore
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* [[OSBYTE &B3|OSBYTE &B3]] - Master ROM polling semaphore location
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* [[Paged ROM service calls]]
  
[[User:Jgharston|Jgharston]] 22:34, 26 May 2009 (UTC)
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[[User:Jgharston|Jgharston]] 22:30, 26 May 2009 (UTC)

Revision as of 02:40, 15 December 2013

OSBYTE &B9 (185) - Read/Write MOS copy of palette register/ROM polling semaphore

   On the BBC, B+ and Master, this contains the MOS's copy of the palette
   register in the video ULA.
   
   On the Electron there is no video ULA, and this location contains the ROM
   polling semaphore. When the semaphore is non-zero the 100Hz ROM service
   call &15 is sent to ROMs. The semaphore is normally accessed with *FX23
   to increment it and *FX24 to decrement it.

See Also

Jgharston 22:30, 26 May 2009 (UTC)