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BLITTER KEY POINTS
This is a list of some key points that should be remembered when programming the
blitter.
o Write BLTSIZE last; writing this register starts the blit.
o Modulos and pointers are in bytes; width is in words and height is in pixels. The least
significant bit of all pointers and modules is ignored.
o The order of operations in the blitter is masking, shifting, logical combination of sources,
area fill, and zero nag setting.
o In ascending mode, the blitter increments the pointers, adds the modules, and shifts to
the right.
o In descending mode, the blitter decrements the pointers, subtracts the modules, and
shifts to the left.
o Area fill only works correctly in descending mode.
o Check BLTDONE before writing blitter registers or using the results of a blit.
o Shifts are done on immediate data as soon as it is loaded.
EXAMPLE: ClearMem
;
; Blitter example - memory clear
;
include 'exec/types.i'
include 'hardware/custom.i'
include 'hardware/dmabits.i'
include 'hardware/blit.i'
include 'hardware/hw examples.i"
xref _custom
;
; Wait for previous blit to complete.
;
waitblit:
btst.b #DMAB_BLTDONE-8,DMACONR(a1)
waitblit2:
btst.b #DMAB_BLTDONE-8,DMACONR(a1)
bne waitblit2
rts
;
; This routine uses a side effect in the blitter. When each
- Blitter Hardware 195 -
Содержание Amiga A1000
Страница 1: ...AMIGA HARDWARE REFERENCE MANUAL 1992 Commodore Business Machines Amiga 1200 PAL...
Страница 20: ...Figure 1 1 Block Diagram for the Amiga Computer Family Introduction 11...
Страница 21: ...12 Introduction...
Страница 72: ...Figure 3 12 A dual Playfield display Playfield Hardware 63...
Страница 87: ...Figure 3 24 Horizontal Scrolling 78 playfield hardware...
Страница 101: ...92 Playfield Hardware...
Страница 199: ...Figure 6 9 DMA time slot allocation 190 Blitter hardware...
Страница 203: ...Figure 6 13 Blitter Block Diagram 194 Blitter Hardware...
Страница 229: ...220 System Control Hardware...
Страница 246: ...Figure 8 8 Chinon Timing diagram cont Interface Hardware 237...
Страница 265: ...256 Interface Hardware...
Страница 289: ...280 Appendix A...
Страница 297: ...288 Appendix B...
Страница 298: ...APPENDIX C CUSTOM CHIP PIN ALLOCATION LIST NOTE Means an active low signal Appendix C 289...
Страница 302: ...APPENDIX D SYSTEM MEMORY MAP Appendix D 293...
Страница 343: ...334 Appendix F...
Страница 351: ...342 Appendix G...
Страница 361: ...352 Appendix H...
Страница 367: ...358 Appendix I...