Atari ST series - Page 193

Drvmap
Find Valid Drive Numbers
Drvmap() Opcode = 10
D r v m a p () m a y b e u se d to d isc o v er w h a t disk d riv es a re cu rre n tly a t
ta ch ed .
C macro format
lo ng driv es;
d riv es = D r v m a p ();
Machine language format
m o v e.w # 1 0 , - (sp)
trap # 1 3
ad d q .l # 2 ,s p
Inputs
N o ne
Results
DO d riv es lo n g A bit fla g th a t in dicates w h ich d riv es are co n n ec te d .
E ac h bit co rre sp o n d s to a d ifferen t d riv es, w ith bit 0
stan d in g for d riv e A :, b it 1 for d riv e B :, an d so o n . A
1 in a bit p o sitio n m ea n s th e d riv e is co n n ec te d ,
w h ile a 0 m ea n s it is n 't. If d riv e A : is p re se n t, driv e
B: is alw a ys p re s en t also , b ec au se if th ere is n o p h y s 
ical B d riv e, th e sy ste m u ses driv e A : a s a log ical
d riv e B :.
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