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One of the features of the Copper is its ability to WAIT for a specific video beam position,
then MOVE data into a system register. During the WAIT period, the Copper examines the
contents of the video beam position counter directly. This means that while the Copper is
waiting for the beam to reach a specific position, it does not use the memory bus at all.
Therefore, the bus is freed for use by the other DMA channels or by the 68000.
When the WAIT condition has been satisfied, the Copper steals memory cycles from either
the blitter or the 68000 to move the specified data into the selected special-purpose
register.
The Copper is a two-cycle processor that requests the bus only during odd-numbered
memory cycles. This prevents collision with audio, disk, refresh, sprites, and most low-
resolution display DMA access, all of which use only the even-numbered memory cycles.
The Copper, therefore, needs priority over only the 68000 and the blitter (the DMA
channel that handles animation, line drawing, and polygon filling).
As with all the other DMA channels in the Amiga system, the Copper can retrieve its
instructions only from the chip RAM area of system memory.
ABOUT THIS CHAPTER
In this chapter, you will learn how to use the special Copper instruction set to organize
mid-screen register value modifications and pointer register set-up during the vertical
blanking interval. The chapter shows how to organize Copper instructions into Copper
lists, how to use Copper lists in interlaced mode, and how to use the Copper with the
blitter. The Copper is discussed in this chapter in a general fashion. The chapters that deal
with playfields, sprites, audio, and the blitter contain more specific suggestions for using
the Copper.
WHAT IS A COPPER INSTRUCTION?
As a coprocessor, the Copper adds its own instruction set to the instructions already
provided by the 68000. The Copper has only three instructions, but you can do a lot with
them:
o WAIT for a specific screen position specified as x and y co-ordinates.
o MOVE n immediate data value into one of the special-purpose registers.
o SKIP the next instruction if the video beam has already reached a specified screen
position.
- 14 Coprocessor Hardware -
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...