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.
This change introduces a new command line flag, '-b', that cause the
simulator to halt on the `BRK` instruction. By default, however, the
simulator will no longer halt on `BRK`.
As before, this behavior can be toggled in the preferences at run-time.
A bug caused the video window to repaint only when the cursor was
blinking. This meant that if the cursor was disabled, the window would
never update!
This change removes the repaint logic from the cursor blinking timer,
and instead puts it into its own periodic timer callback that runs
independently of cursor blink.
* On Linux GTK+, the small text fields in the Status Panel displayed a
large inner margin, cutting off text. This change forces Java to use the
Metal look-and-feel for these fields, which forces no default inner
margin.
- Added more CRTC information to the README file.
- Added unit tests for the CRTC.
- Implemented register read for cursor position in the CRTC.
- Bundling a new version of jterminal that has correct backspace
behavior.
Introduces several changes requested by Mario Keller. The simulator now has a variable step count that can be selected by a drop-down box on the main window. This change also displays ASCII characters in the Memory window.
- Added tooltip text to status panel.
- Memory is no longer cleared on reset.
- Console can now receive key-strokes even while the simulator is
stopped (for single-stepping programs that require interaction)
- Updated screenshots with bug-fixed version.
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.
Adds a new view that displays a single page of memory (user selectable)
and allows direct editing of memory contents.
Also fixes several minor bugs, including one that prevented the status
pane from updating after each manual step.
- If a default ROM image ("rom.bin") isn't available at startup, the
simulator will now create and load a 16KB R/W memory at the ROM
location, so resets will work even without a ROM loaded.
- Cleaned up the way simulator UI state is updated when the run loop
exits.
I was alarmed to discover just how slow `String.format()` is for doing
integer to hex conversions. Now that a trace window has been added to
Symon, it became especially clear that I needed a more efficient way to
handle it.
I looked into using `Integer.toHexString()`, but I would have had to
wrap it to do zero-padding, so I decided to just bite the bullet and do
my own with a lookup table. The implementation in `HexUtil` is just as
fast as `Integer.toHexString()`, but also zero-pads appropriately.
Combined with Java's `+` String concatenation, it seems perfectly
adequate.
For yet better performance with the trace window, it would make a lot of
sense to special-case stepping so that it just pops the top line off the
log, and appends to the bottom, rather than re-stringifying the entire
trace log each time. This will be a future enhancement.
Seth Morabito