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!6502Em/Docs/Technical
This website contains an archive of files for the Acorn Electron, BBC Micro, Acorn Archimedes, Commodore 16 and Commodore 64 computers, which Dominic Ford has rescued from his private collection of floppy disks and cassettes.
Some of these files were originally commercial releases in the 1980s and 1990s, but they are now widely available online. I assume that copyright over them is no longer being asserted. If you own the copyright and would like files to be removed, please contact me.
| Tape/disk: | Home » Archimedes archive » Zipped Apps » 6502em |
| Filename: | !6502Em/Docs/Technical |
| Read OK: | ✔ |
| File size: | 0754 bytes |
| Load address: | 0000 |
| Exec address: | 0000 |
File contents
6502Em: The Emulation ===================== The processor emulated is the 65C12 as in the Master 128, with the following exceptions: o Opcodes &07, &0B, &4B, &87, &DC emulate the respective 6502 undocumented opcodes o Opcode &07 when in Sideways ROM issues a SWI under RISC OS (see 'Opcode07') o The timing of opcodes when in BCD mode is as for the original 6502, not the 65C12 o The flags are not fully emulated in BCD mode o A few of the opcode timings are not quite correct for 1MHz memory accesses o Opcodes &03 and &23 are used for internal purposes by the emulator o The JMP (&xxFF) bug is emulated for the BBC and Electron modes NB "Unused" Opcodes are defined to be NOPs The extra Rockwell opcodes are not supported The 6845 CRTC ------------- Registers 1,6,10,11,12,13,14,15 are fully emulated Register 9 is partially emulated The Video ULA ------------- Fully emulated, except for "mode 8" Gap modes are displayed without gaps The 6850 ACIA & Serial ULA -------------------------- Not Emulated The Paged ROM Select Register (ROMSEL) -------------------------------------- Fully Emulated Supports ROM or RAM in any of the 16 banks The 6522 VIAs ------------- The VIAs are fully emulated except for the shift register The System VIA -------------- Interrupts supported from 6845, keyboard and the two timers Interrupts from 7002 ADC and light pen not supported Keyboard, sound and the screen wrap address supported Caps Lock LED emulated Shift Lock LED not supported The User Via ------------ Interrupts supported from the 2 timers and printer. User port not supported The 7002 ADC ------------ Returns the mouse's position on both channels unless a joystick module is loaded that conforms to Acorn's Joystick SWI specifications. Econet & Disc Hardware ---------------------- Not Emulated Tube Hardware ------------- Not Emulated
00000000 36 35 30 32 45 6d 3a 20 54 68 65 20 45 6d 75 6c |6502Em: The Emul| 00000010 61 74 69 6f 6e 0a 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d |ation.==========| 00000020 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 0a 0a 54 68 65 |===========..The| 00000030 20 70 72 6f 63 65 73 73 6f 72 20 65 6d 75 6c 61 | processor emula| 00000040 74 65 64 20 69 73 20 74 68 65 20 36 35 43 31 32 |ted is the 65C12| 00000050 20 61 73 20 69 6e 20 74 68 65 0a 4d 61 73 74 65 | as in the.Maste| 00000060 72 20 31 32 38 2c 20 77 69 74 68 20 74 68 65 20 |r 128, with the | 00000070 66 6f 6c 6c 6f 77 69 6e 67 20 65 78 63 65 70 74 |following except| 00000080 69 6f 6e 73 3a 0a 0a 6f 20 4f 70 63 6f 64 65 73 |ions:..o Opcodes| 00000090 20 26 30 37 2c 20 26 30 42 2c 20 26 34 42 2c 20 | &07, &0B, &4B, | 000000a0 26 38 37 2c 20 26 44 43 20 65 6d 75 6c 61 74 65 |&87, &DC emulate| 000000b0 20 74 68 65 0a 20 20 72 65 73 70 65 63 74 69 76 | the. respectiv| 000000c0 65 20 36 35 30 32 20 75 6e 64 6f 63 75 6d 65 6e |e 6502 undocumen| 000000d0 74 65 64 20 6f 70 63 6f 64 65 73 0a 6f 20 4f 70 |ted opcodes.o Op| 000000e0 63 6f 64 65 20 26 30 37 20 77 68 65 6e 20 69 6e |code &07 when in| 000000f0 20 53 69 64 65 77 61 79 73 20 52 4f 4d 20 69 73 | Sideways ROM is| 00000100 73 75 65 73 20 61 20 53 57 49 0a 20 20 75 6e 64 |sues a SWI. und| 00000110 65 72 20 52 49 53 43 20 4f 53 20 28 73 65 65 20 |er RISC OS (see | 00000120 27 4f 70 63 6f 64 65 30 37 27 29 0a 6f 20 54 68 |'Opcode07').o Th| 00000130 65 20 74 69 6d 69 6e 67 20 6f 66 20 6f 70 63 6f |e timing of opco| 00000140 64 65 73 20 77 68 65 6e 20 69 6e 20 42 43 44 20 |des when in BCD | 00000150 6d 6f 64 65 20 69 73 0a 20 20 61 73 20 66 6f 72 |mode is. as for| 00000160 20 74 68 65 20 6f 72 69 67 69 6e 61 6c 20 36 35 | the original 65| 00000170 30 32 2c 20 6e 6f 74 20 74 68 65 20 36 35 43 31 |02, not the 65C1| 00000180 32 0a 6f 20 54 68 65 20 66 6c 61 67 73 20 61 72 |2.o The flags ar| 00000190 65 20 6e 6f 74 20 66 75 6c 6c 79 20 65 6d 75 6c |e not fully emul| 000001a0 61 74 65 64 20 69 6e 20 42 43 44 20 6d 6f 64 65 |ated in BCD mode| 000001b0 0a 6f 20 41 20 66 65 77 20 6f 66 20 74 68 65 20 |.o A few of the | 000001c0 6f 70 63 6f 64 65 20 74 69 6d 69 6e 67 73 20 61 |opcode timings a| 000001d0 72 65 20 6e 6f 74 20 71 75 69 74 65 0a 20 20 63 |re not quite. c| 000001e0 6f 72 72 65 63 74 20 66 6f 72 20 31 4d 48 7a 20 |orrect for 1MHz | 000001f0 6d 65 6d 6f 72 79 20 61 63 63 65 73 73 65 73 0a |memory accesses.| 00000200 6f 20 4f 70 63 6f 64 65 73 20 26 30 33 20 61 6e |o Opcodes &03 an| 00000210 64 20 26 32 33 20 61 72 65 20 75 73 65 64 20 66 |d &23 are used f| 00000220 6f 72 20 69 6e 74 65 72 6e 61 6c 0a 20 20 70 75 |or internal. pu| 00000230 72 70 6f 73 65 73 20 62 79 20 74 68 65 20 65 6d |rposes by the em| 00000240 75 6c 61 74 6f 72 0a 6f 20 54 68 65 20 4a 4d 50 |ulator.o The JMP| 00000250 20 28 26 78 78 46 46 29 20 62 75 67 20 69 73 20 | (&xxFF) bug is | 00000260 65 6d 75 6c 61 74 65 64 20 66 6f 72 20 74 68 65 |emulated for the| 00000270 20 0a 20 20 42 42 43 20 61 6e 64 20 45 6c 65 63 | . BBC and Elec| 00000280 74 72 6f 6e 20 6d 6f 64 65 73 0a 0a 4e 42 20 22 |tron modes..NB "| 00000290 55 6e 75 73 65 64 22 20 4f 70 63 6f 64 65 73 20 |Unused" Opcodes | 000002a0 61 72 65 20 64 65 66 69 6e 65 64 20 74 6f 20 62 |are defined to b| 000002b0 65 20 4e 4f 50 73 0a 20 20 20 54 68 65 20 65 78 |e NOPs. The ex| 000002c0 74 72 61 20 52 6f 63 6b 77 65 6c 6c 20 6f 70 63 |tra Rockwell opc| 000002d0 6f 64 65 73 20 61 72 65 20 6e 6f 74 20 73 75 70 |odes are not sup| 000002e0 70 6f 72 74 65 64 0a 0a 54 68 65 20 36 38 34 35 |ported..The 6845| 000002f0 20 43 52 54 43 0a 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d | CRTC.----------| 00000300 2d 2d 2d 0a 0a 52 65 67 69 73 74 65 72 73 20 31 |---..Registers 1| 00000310 2c 36 2c 31 30 2c 31 31 2c 31 32 2c 31 33 2c 31 |,6,10,11,12,13,1| 00000320 34 2c 31 35 20 61 72 65 20 66 75 6c 6c 79 20 65 |4,15 are fully e| 00000330 6d 75 6c 61 74 65 64 0a 52 65 67 69 73 74 65 72 |mulated.Register| 00000340 20 39 20 69 73 20 70 61 72 74 69 61 6c 6c 79 20 | 9 is partially | 00000350 65 6d 75 6c 61 74 65 64 0a 0a 54 68 65 20 56 69 |emulated..The Vi| 00000360 64 65 6f 20 55 4c 41 0a 2d 2d 2d 2d 2d 2d 2d 2d |deo ULA.--------| 00000370 2d 2d 2d 2d 2d 0a 0a 46 75 6c 6c 79 20 65 6d 75 |-----..Fully emu| 00000380 6c 61 74 65 64 2c 20 65 78 63 65 70 74 20 66 6f |lated, except fo| 00000390 72 20 22 6d 6f 64 65 20 38 22 0a 47 61 70 20 6d |r "mode 8".Gap m| 000003a0 6f 64 65 73 20 61 72 65 20 64 69 73 70 6c 61 79 |odes are display| 000003b0 65 64 20 77 69 74 68 6f 75 74 20 67 61 70 73 0a |ed without gaps.| 000003c0 0a 54 68 65 20 36 38 35 30 20 41 43 49 41 20 26 |.The 6850 ACIA &| 000003d0 20 53 65 72 69 61 6c 20 55 4c 41 0a 2d 2d 2d 2d | Serial ULA.----| 000003e0 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------| 000003f0 2d 2d 2d 2d 2d 2d 0a 0a 4e 6f 74 20 45 6d 75 6c |------..Not Emul| 00000400 61 74 65 64 0a 0a 54 68 65 20 50 61 67 65 64 20 |ated..The Paged | 00000410 52 4f 4d 20 53 65 6c 65 63 74 20 52 65 67 69 73 |ROM Select Regis| 00000420 74 65 72 20 28 52 4f 4d 53 45 4c 29 0a 2d 2d 2d |ter (ROMSEL).---| 00000430 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------| * 00000450 2d 2d 2d 0a 0a 46 75 6c 6c 79 20 45 6d 75 6c 61 |---..Fully Emula| 00000460 74 65 64 0a 53 75 70 70 6f 72 74 73 20 52 4f 4d |ted.Supports ROM| 00000470 20 6f 72 20 52 41 4d 20 69 6e 20 61 6e 79 20 6f | or RAM in any o| 00000480 66 20 74 68 65 20 31 36 20 62 61 6e 6b 73 0a 0a |f the 16 banks..| 00000490 54 68 65 20 36 35 32 32 20 56 49 41 73 0a 2d 2d |The 6522 VIAs.--| 000004a0 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 0a 0a 54 68 65 |-----------..The| 000004b0 20 56 49 41 73 20 61 72 65 20 66 75 6c 6c 79 20 | VIAs are fully | 000004c0 65 6d 75 6c 61 74 65 64 20 65 78 63 65 70 74 20 |emulated except | 000004d0 66 6f 72 20 74 68 65 20 73 68 69 66 74 20 72 65 |for the shift re| 000004e0 67 69 73 74 65 72 0a 0a 54 68 65 20 53 79 73 74 |gister..The Syst| 000004f0 65 6d 20 56 49 41 0a 2d 2d 2d 2d 2d 2d 2d 2d 2d |em VIA.---------| 00000500 2d 2d 2d 2d 2d 0a 0a 49 6e 74 65 72 72 75 70 74 |-----..Interrupt| 00000510 73 20 73 75 70 70 6f 72 74 65 64 20 66 72 6f 6d |s supported from| 00000520 20 36 38 34 35 2c 20 6b 65 79 62 6f 61 72 64 20 | 6845, keyboard | 00000530 61 6e 64 20 74 68 65 20 74 77 6f 20 74 69 6d 65 |and the two time| 00000540 72 73 0a 49 6e 74 65 72 72 75 70 74 73 20 66 72 |rs.Interrupts fr| 00000550 6f 6d 20 37 30 30 32 20 41 44 43 20 61 6e 64 20 |om 7002 ADC and | 00000560 6c 69 67 68 74 20 70 65 6e 20 6e 6f 74 20 73 75 |light pen not su| 00000570 70 70 6f 72 74 65 64 0a 4b 65 79 62 6f 61 72 64 |pported.Keyboard| 00000580 2c 20 73 6f 75 6e 64 20 61 6e 64 20 74 68 65 20 |, sound and the | 00000590 73 63 72 65 65 6e 20 77 72 61 70 20 61 64 64 72 |screen wrap addr| 000005a0 65 73 73 20 73 75 70 70 6f 72 74 65 64 0a 43 61 |ess supported.Ca| 000005b0 70 73 20 4c 6f 63 6b 20 4c 45 44 20 65 6d 75 6c |ps Lock LED emul| 000005c0 61 74 65 64 0a 53 68 69 66 74 20 4c 6f 63 6b 20 |ated.Shift Lock | 000005d0 4c 45 44 20 6e 6f 74 20 73 75 70 70 6f 72 74 65 |LED not supporte| 000005e0 64 0a 0a 54 68 65 20 55 73 65 72 20 56 69 61 0a |d..The User Via.| 000005f0 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 0a 0a 49 6e |------------..In| 00000600 74 65 72 72 75 70 74 73 20 73 75 70 70 6f 72 74 |terrupts support| 00000610 65 64 20 66 72 6f 6d 20 74 68 65 20 32 20 74 69 |ed from the 2 ti| 00000620 6d 65 72 73 20 61 6e 64 20 70 72 69 6e 74 65 72 |mers and printer| 00000630 2e 0a 55 73 65 72 20 70 6f 72 74 20 6e 6f 74 20 |..User port not | 00000640 73 75 70 70 6f 72 74 65 64 0a 0a 54 68 65 20 37 |supported..The 7| 00000650 30 30 32 20 41 44 43 0a 2d 2d 2d 2d 2d 2d 2d 2d |002 ADC.--------| 00000660 2d 2d 2d 2d 0a 0a 52 65 74 75 72 6e 73 20 74 68 |----..Returns th| 00000670 65 20 6d 6f 75 73 65 27 73 20 70 6f 73 69 74 69 |e mouse's positi| 00000680 6f 6e 20 6f 6e 20 62 6f 74 68 20 63 68 61 6e 6e |on on both chann| 00000690 65 6c 73 20 75 6e 6c 65 73 73 20 61 0a 6a 6f 79 |els unless a.joy| 000006a0 73 74 69 63 6b 20 6d 6f 64 75 6c 65 20 69 73 20 |stick module is | 000006b0 6c 6f 61 64 65 64 20 74 68 61 74 20 63 6f 6e 66 |loaded that conf| 000006c0 6f 72 6d 73 20 74 6f 20 41 63 6f 72 6e 27 73 0a |orms to Acorn's.| 000006d0 4a 6f 79 73 74 69 63 6b 20 53 57 49 20 73 70 65 |Joystick SWI spe| 000006e0 63 69 66 69 63 61 74 69 6f 6e 73 2e 0a 0a 45 63 |cifications...Ec| 000006f0 6f 6e 65 74 20 26 20 44 69 73 63 20 48 61 72 64 |onet & Disc Hard| 00000700 77 61 72 65 0a 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |ware.-----------| 00000710 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 0a 0a 4e 6f 74 |-----------..Not| 00000720 20 45 6d 75 6c 61 74 65 64 0a 0a 54 75 62 65 20 | Emulated..Tube | 00000730 48 61 72 64 77 61 72 65 0a 2d 2d 2d 2d 2d 2d 2d |Hardware.-------| 00000740 2d 2d 2d 2d 2d 2d 0a 0a 4e 6f 74 20 45 6d 75 6c |------..Not Emul| 00000750 61 74 65 64 |ated| 00000754
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