OSWORD &21

OSWORD &21 (33 ) - Execute code in I/O processor TubeLink

On entry:
 XY!0=I/O address
 XY?4=A register
 XY?5=X register
 XY?6=Y register
 XY?7=P register (only bit 0 significant - Carry flag)
 XY?8=semaphore byte
On exit:
 If the code has been executed, the semaphore byte is
 incremented by one. Extended I/O addresses are used.
 &FFrrxxxx specifies ROM &rr, &FFFExxxx specifies shadow
 screen memory. Returned register values are returned in
 control block.

See Also

• http://mdfs.net/Docs/Comp/BBC/Oswords

Jgharston 13:31, 26 May 2009 (UTC)