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CIAAPRA/CIABPRB - DISK SELECTION, CONTROL AND SENSING
The following Table lists how 8520 chip bits used by the disk subsystem. Bits labelled "PA"
are input bits in CIAAPRA ($BFE001). Bits labelled "PB" are output bits located in CIAAPRB
($BFD100). More information on how the 8520 chips operate can be found in Appendix F.
Table 8-5: Disk Subsystem
Bit Name Function
PA5 DSKRDY* Disk ready (active low). The drive will pull this line
low when the motor is known to be rotating at full
speed. This signal is only valid when the motor is ON,
at other times configuration information may obscure
the meaning of this input.
PA4 DSKTRACK0* Track zero detect. The drive will pull this line low
when the disk heads are positioned over track zero.
Software must not attempt to step outwards when this
signal is active. Some drives will refuse to step,
others will attempt the step, possibly causing
alignment damage.
All new drives must refuse to step outward in this
condition.
PA3 DSKPROT* Disk is write protected (active low).
PA2 DSKCHANGE* Disk has been removed from the drive. The signal goes
low whenever a disk is removed. It remains low until a
disk is inserted AND a step pulse is received.
PB7 DSKMOTOR* Disk motor control (active low). This signal is
nonstandard on the Amiga system. Each drive will latch
the motor signal at the time its select signal turns
on. The disk drive motor will stay in this state until
the next time select turns on. DSKMOTOR* also controls
the activity light on the front of the disk drive.
All software that selects drives must set up the motor
signal before selecting any drives. The drive will
"remember" the state of its motor when it is not
selected. All drive motors turn off after system reset.
- 238 Interface 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...