OSBYTE &B3

OSBYTE &B3 (179) - Read/Write primary OSHWM/ROM polling semaphore

   On the BBC, B+ and Electron, this contains the page number of OSHWM
   ignoring any font implosions and explosions.
   
   On the Master onwards, the font is always exploded, 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

• OSBYTE &16 - Increment ROM polling semaphore
• OSBYTE &17 - Decrement ROM polling semaphore
• OSBYTE &B9 - Electron ROM polling semaphore location
• Paged ROM service calls

Jgharston 22:30, 26 May 2009 (UTC)