Atari ST series - Page 242

Blitmode
Get/Set Blitter Configuration
Blitmode() Opcode = 64
T his fu nction is u se d to find o u t if a blitter ch ip is availa ble, an d w h eth er it
is b ein g u sed fo r d raw in g ro utin e s. If th e b litter ch ip is p res en t, th is fu n c
tion m a y a lso be u se d to ch o o se b etw e en h a rd w a re blittin g o r so ftw a re
em u latio n m o d e.
C macro format
# d e f m e B litm o d e(a) xb io s(6 4,a)
in t sta tu s, v alu e;
sta tu s = B litm o d e(v alu e);
Machine language format
m o v e .w
va lu e, - (sp)
m o v e .w
# 6 4 , - (sp )
trap
# 1 4
ad d q .l
# 4 ,s p
Inputs
value
w o rd
A bit flag u sed to s et th e blitter co n fig u
ratio n . A v alu e of - 1 is u sed to re ad , n o t
ch an g e , th e co n fig u ra tion .
T h e bit v alu es fo r th e v alu e flag a re :
Bit Number Function
0 S et blit m o d e
0 = U se s oftw a re blit ro u tin es
1 = U se blitter h ard w a re
1 - 1 4 U n de fin ed , re serv e d
15 M u st b e 0
Results
DO sta tu s w o rd A bit flag th at re tu rn s th e blitter co n fig uratio n as it
sto od p rio r to th e se t o p eratio n .
T h e sta tu s bit v alu es are :
Bit Number Description
0 C u rre n t blit m o d e
0 = U sin g so ftw a re blit ro u tin es
1 = U sin g b litter h a rd w are
1 Blitter ch ip availab ility
0 = B litter ch ip n o t availab le
1 = B litter ch ip is in stalled
2 - 1 4 U n d efin ed , re se rv ed
15 A 0 is alw ay s re tu rn ed
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