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As you create Copper instruction lists, note that the final list must be in the same order as
that in which the video beam creates the display. The video beam traverses the screen
from position (0,0) in the upper left hand corner of the screen to the end of the display
(226,262) NTSC (or (226,312) PAL) in the lower right hand corner. The first 0 in (0,0)
represents the x position. The second 0 represents the y position. For example, an
instruction that does something at position (0,100) should come after an instruction that
affects the display at position (0,60).
NOTE
Given the form of the WAIT instruction, you can sometimes get away with not sorting the
list in strict video beam order. The WAIT instruction causes the Copper to wait until the
value in the beam counter is equal to or greater than the value in the instruction.
This means, for example, if you have instructions following each other like this:
WAIT for position (64,64)
MOVE data
WAIT for position (60,60)
MOVE data
The Copper will perform both moves, even though the instructions are out of sequence.
The "greater than" specification prevents the Copper from locking up if the beam has
already passed the specified position. A side effect is that the second MOVE below will be
performed:
WAIT for position (60,60)
MOVE data
WAIT for position (60,60)
MOVE data
At the time of the second WAIT in this sequence, the beam counters will be greater than
the position shown in the instructions. Therefore, the second MOVE will also be performed.
Note also that the above sequence of instructions could just as easily be
WAIT for position (60,60)
MOVE data
MOVE data
because multiple MOVEs can follow a single WAIT.
- Coprocessor Hardware 23 -
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...