Altirra Hardware Reference Manual by Avery Lee Version: 04/27/14 Altirra Hardware Reference Manual Created by Avery Lee Table of Contents 1.1. Introduction.................................................................................................................................................... 6 1.2. What's new in this edition.............................................................................................................................. 7 1.3. Conventions in this manual........................................................................................................................... 9 1.4. Basic characteristics................................................................................................................................... 10 2. CPU..................................................................................................................................................................... 13 2.1. Registers..................................................................................................................................................... 14 2.2. Decimal mode............................................................................................................................................. 14 2.3. Cycle timing................................................................................................................................................. 15 2.4. Interrupts..................................................................................................................................................... 16 2.5. Examples..................................................................................................................................................... 18 2.6. Further reading............................................................................................................................................ 18 3. System control..................................................................................................................................................... 19 3.1. System Reset button................................................................................................................................... 20 3.2. Peripheral Interface Adapter (PIA).............................................................................................................. 20 3.3. Memory system........................................................................................................................................... 21 3.4. Bank switching............................................................................................................................................ 22 3.5. Extended memory....................................................................................................................................... 23 3.6. Parallel Bus Interface (PBI)......................................................................................................................... 24 3.7. Miscellaneous connections......................................................................................................................... 24 3.8. Examples..................................................................................................................................................... 25 3.9. Further reading............................................................................................................................................ 25 4. ANTIC.................................................................................................................................................................. 26 4.1. Basic operation............................................................................................................................................ 27 4.2. Playfield....................................................................................................................................................... 27 4.3. Character modes......................................................................................................................................... 29 4.4. Mapped (bitmap) modes............................................................................................................................. 31 4.5. Display list................................................................................................................................................... 32 4.6. Horizontal scrolling...................................................................................................................................... 35 4.7. Non-maskable interrupts............................................................................................................................. 38 4.8. WSYNC....................................................................................................................................................... 40 4.9. VCOUNT..................................................................................................................................................... 42 4.10. Playfield DMA............................................................................................................................................ 42 4.11. Abnormal Playfield DMA............................................................................................................................ 43 4.12. Player/missile DMA................................................................................................................................... 45 4.13. DMA timing................................................................................................................................................ 46 4.14. Cycle counting example............................................................................................................................ 56 4.15. Further reading.......................................................................................................................................... 59 5. POKEY................................................................................................................................................................ 60 5.1. Addressing................................................................................................................................................... 61 5.2. Initialization.................................................................................................................................................. 61 5.3. Sound generation........................................................................................................................................ 61 5.4. Serial port.................................................................................................................................................... 63 5.5. Clock generation......................................................................................................................................... 67 5.6. Pseudo-random number generators........................................................................................................... 67 5.7. Interrupts..................................................................................................................................................... 67 5.8. Keyboard scan............................................................................................................................................ 69 5.9. Examples..................................................................................................................................................... 70 5.10. Further reading.......................................................................................................................................... 71 6. CTIA/GTIA........................................................................................................................................................... 72 6.1. Color registers............................................................................................................................................. 73 Chapter - 2 Altirra Hardware Reference Manual Created by Avery Lee 6.2. Player/missile graphics............................................................................................................................... 73 6.3. Collision detection....................................................................................................................................... 76 6.4. Priority control............................................................................................................................................. 77 6.5. High resolution mode (ANTIC modes 2, 3, and F)...................................................................................... 79 6.6. GTIA special modes.................................................................................................................................... 79 6.7. Cycle timing................................................................................................................................................. 81 6.8. General purpose I/O.................................................................................................................................... 83 6.9. Further reading...........................................................................................................................................