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MASTER INTERRUPT ENABLE
Bit 14 of the interrupt registers (INTEN) is for interrupt enable. This is the master
interrupt enable bit. If this bit is a 0, it disables all other interrupts. You may wish to clear
this bit to temporarily disable all interrupts to do some critical processing task.
NOTE
This bit is used for enable/disable only. It creates no interrupt request.
EXTERNAL INTERRUPTS
Bits 13 and 3 of the interrupt registers are reserved for external interrupts.
Bit 13, EXTER, becomes a 1 when the system line called INT6* becomes a logic 0. Bit 13
generates a level 6 interrupt.
Bit 3, PORTS, becomes a 1 when the system line called INT2* becomes a logic 0. Bit 3
causes a level 2 interrupt.
VERTICAL BLANKING INTERRUPT
Bit 5, VERTB, causes an interrupt at line 0 (start of vertical blank) of the video display
frame. The system is often required to perform many different tasks during the vertical
blanking interval. Among these tasks are the updating of various pointer registers,
rewriting lists of Copper tasks when necessary, and other system-control operations.
The minimum time of vertical blanking is 20 horizontal scan lines for an NTSC system and
25 horizontal scan lines for a PAL system. The range starts at line 0 and ends at line 20
for NTSC or line 25 for PAL. After the minimum vertical blanking range, you can control
where the display actually starts by using the DIWSTRT (display window start) register to
extend the effective vertical blanking time. See Chapter 3, "Playfield Hardware," for more
information on DIWSTRT.
If you find that you still require additional time during vertical blanking, you can use the
Copper to create a level 3 interrupt. This Copper interrupt would be timed to occur just
after the last line of display on the screen (after the display window stop which you have
defined by using the DIWSTOP register).
- 214 System Control 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...