Atari ST series - Page 228

Giaccess
Read/Write Sound Chip
Giaccess()
Opcode = 28
T his fu nction allow s y o u to rea d o r ch a n g e a n y reg ister in th e P ro g ra m m a 
ble S o un d G en e ra to r (P SG ) ch ip .
C macro format
ch ar re g va lu e, va lu e;
in t re gn u m ;
reg v alu e = G iacce ss(v alu e, reg n u m );
Machine language format
m o v e .w # r e g n u m , - (sp )
m o v e .w # v a lu e , - (sp )
m o v e .w # 2 8 , - (sp )
tra p # 1 4
ad d q .l # 6 ,s p
Results
DO reg v alu e b y te T h e n u m b er sto re d in th e reg ister a t th e e n d o f th e
call.
See also
O n g ib it(), O ffg ib it()
Inputs
re g n u m w o rd
T h e n u m b er o f th e re gister to rea d o r
ch a n ge . If y o u 're re a d in g th e re g iste r, u se
th e re g ister n u m b er (0 -1 5 ). T o ch a n g e the
reg iste r, u se th e re g iste r nu m b er + 128
(1 2 8 -1 4 3 ).
T h e n ew 8-b it n u m b er to g o in to th e re g
ister.
v alu e
b y te
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