Bug Fixes:
- Fixed several bugs in the CPU that caused processor status flags to
be set incorrectly. Instructions affected were: STA, STX, STY, CMP,
CPX, CPY, BIT.
- Made some internal-use-only methods on the CPU class private.
- Fixed incorrect disassembly of (Indirect,X) and (Indirect),Y
instructions. Although this didn't affect behavior, it certainly
caused me some confusion in debugging.
- Added missing "BCS" instruction to instruction table.
Enhancements:
- Now includes a full version of Lee Davison's Enhanced 6502 BASIC
bundled as source code and a ROM image. Get that REAL COMPUTER
EXPERIENCE!(tm)
- If a file named "rom.bin" exists in the same directory where the
simulator is executed, it will be loaded at addresses $d000-$ffff.
- Gave the CPU an idle loop to make simulated timing a little more
realistic (but this is still an area needing major improvement)
- Changed the CPU's toString() method to give better debugging output.
- Added a small typeahead buffer to the Console.
- Better exception messaging.
Misc:
- Bumped version to 0.5, updated README.
This change introduces simulated baud rates in the ACIA. Baud rate is controlled just as in the real 6551, by writing to the ACIA's control register. Baud rates between 50 and 19,200 baud are selectable. A baud rate of 0 has special meaning, and turns off all simulated baud rate delays (on a real 6551, this means to use an external clock instead of the internal baud rate generator)
A busy-wait loop between steps in the simulator control program has also been added. This uses the high-resolution 'System.nanoTime()' call to wait a specific number of nanoseconds before continuing. Symon now waits at least 1uS between clock cycles, trying to approach a real 1MHz 6502 in performance. It is far from perfect, but it's better than it was.
Also refactored the status panel to use a BoxLayout, and DRY-up some of the code.
- Added ability to change inner border width of console window.
- Fixed a nasty bug that prevented key press handling.
- Reset now clears the accumulator and index registers.
MOS6551 ACIA at address $C000 which does buffered input and output via the
console. Updated the README with a bit more documentation, and bumped the
version number to 0.1 because I'm impatient.
Seth Morabito