8bitworkshop/src/docs/crtprobe.md

CRT Probe

The CRT Probe shows memory and I/O activity laid out by raster position instead of by address, so you can see what the CPU touches at each point of the display sweep. It is available on platforms that implement startProbing.

The canvas axes are:

• X is the cycle within the scanline.
• Y is the scanline.

Activity is color-coded:

Color	Operation
Grey ramp	Execute (shade reflects stack depth, so call depth is visible)
Blue	Memory write
Cyan	VRAM write
Light blue	I/O write
Green	I/O read
Green fill	Wait
Pink	Interrupt

Illegal operations and DMA reads are drawn in grey. Gaps in the trace are filled with the previous color, so the display does not show false black bands.

The view shows a complete frame, and might be incomplete during debugging.