home *** CD-ROM | disk | FTP | other *** search
- 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
-
- 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
- User & Printer ports 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