Preparing hardware…
Last step
Keyboard and execution
Click the screen to type or paste one line. Enter submits; Backspace edits; Escape or Ctrl-C sends Break; Home sends Clear. Host key repeat is ignored. Leaving the window pauses and releases queued keys.
Reset CPU preserves RAM and device settings. Fresh power-on clears them and keeps the installed ROMs. This profile is untimed: steps are not clock cycles.
Run to address executes normally and pauses before the next boundary at that PC, or after 2,000,000 boundaries. Breakpoints and RAM write watchpoints can stop it earlier. Run, Step, Pause, reset, and leaving the window cancel the target.
Breakpoints
$0000–$FFFF · Stops before the CPU boundary at this PC. Run crosses the breakpoint that just stopped once; a later visit stops again.
RAM write watchpoints
$0000–$7FFF · Stops after a complete instruction or interrupt entry writes this RAM byte, even when its value stays the same. ROM and device writes do not match.
Stops are remembered in this browser, separately from snapshots. Step crosses the current breakpoint. Reset and Restore clear the stop report and keep configured stops. Click a circle in Disassembly to toggle a breakpoint.
About this history
Oldest first. Captures physical RAM writes to every configured watch, even with stopping disabled, Live off, or Changes recording paused. Unchanged writes and interrupt entry are included; reads, ROM, and device writes are excluded. Removing a watch clears its history. Reset, power-on, restoration, and ROM replacement clear all history. Links browse current storage.
RAM and loaded ROM · -- means no storage · I/O is never read
| Routine | Address | Bytes | Instruction | Reference | Comment |
|---|
Push moves down; pull moves up. Words are high byte first. This is a pointer window, not a list of frames; no empty-stack boundary is known.
Push moves down; pull moves up. Words are high byte first. This is a pointer window, not a list of frames; no empty-stack boundary is known.
Recorded changes
Recording · 0 / 500 events retained
CPU address or user action · before → after · newest first
About this log
Values are hex; flags use 0 and 1. Filters only change what is shown. Records every CPU boundary, even with this tab closed. Keeps the latest 500 events.
Pause recording to keep a capture while the CPU runs. Event numbers leave gaps for unrecorded steps. Clear log restarts numbering.
Memory lists actual RAM changes in write order, from instructions and external interrupt entry. Unchanged stores, ROM and device writes are omitted. Reset, power-on, state restoration and successful media replacement clear the log.
No events recorded yet.
From the CPU specification
Previewed storage accesses
Prediction on a private CPU copy; devices are never accessed.
V: SAM sequence · GM: VDG format · CSS: colour set
M: memory · R: clock · TY: map · untimed
| Register / input | PIA 0 | PIA 1 |
|---|
Color BASIC 1.3
No ROM loaded.
Choose the separate 8 KiB Color BASIC 1.3 ROM. The file stays on this device.
Extended BASIC 1.1 · optional
No ROM loaded.
Choose the separate 8 KiB Extended BASIC 1.1 ROM. The file stays on this device.
Changing the extension starts fresh hardware. Use Color BASIC only also forgets the extension.
Before running
What to observe
Selecting a checkpoint only changes the guide. Run stops before its address, or after 2,000,000 boundaries. Breakpoints and RAM write watchpoints can stop it earlier; see Execution or Debugger for the reason. Reaching an address does not verify the setup. Step and Run remain in Execution.
No snapshot saved.
One local checkpoint, replaced by Save. Pause first. Includes RAM, processor, devices, and queued input; restoring requires the same ROMs, including the same empty or loaded extension socket. ROM bytes and panel layout are stored separately.