This change adds a new "Step Over" button, which is enabled
when a "JSR" (Jump to Subroutine) instruction is encountered
while stepping through execution one instruction at a time.
Pressing "Step Over" will continue running instructions until a
corresponding "RTS" (Return from Subroutine) is encountered.
While stepping over a subroutine, the call stack depth is tracked
in an attempt to halt only when the *correct* RTS is encountered.
In other words, it should skip over other subroutines nested
inside the call you want to step over:
```
JSR A # Step over here...
...
JSR B
...
RTS # Returns from 'B', doesn't halt
...
RTS # Returns from 'A', halts after return
```
Implements feature request #18.
- IR field in status panel now correctly displays the next instruction
to be executed, instead of the instruction that was just executed.
- Switched from built-in Java util logger to Logback
- Updated all copyright strings to 2016
The simulator now passes Klaus Dormann's 6502 Functional Test suite for
the first time.
Bug Fixes:
- PHP was not correctly setting the Break bit on the stack copy of the
processor status, so subsequent PLA's would not set the Break status
flag.
- The CPU had swapped NMI and IRQ reset vectors, so RTI was failing.
- BRK was pushing PC + 2 onto the stack, instead of PC + 1
- (Zero Page,X) addressing mode did not correctly wrap on zero page
boundaries.
- The instruction table used for disassembly had addressing modes
of LDA $B9 and $BD reversed. This did not affect behavior, only
disassembly of these instructions.
Other:
- Updated copyright date for 2013.
- Started migrating old JUnit 3 style tests to JUnit 4 annotations.
- The UI layout has changed, and will likely change again in the future.
- Symon can now re-load ROM images from the File menu, under "Load ROM..."
- Font size can be changed under the "View" menu
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.
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