SpritesMind.Net

Reading adress range cause machine lock-up.
What happen exactly when it happen?
Are there signals concerned in this mecanism?
Are thé CPU halten?

Use search engine.

did you look at charles doc, etc... ?
Some addresses are invalid and if you check z80's one you need to request its bus first

A lock up is typically a symptom of nothing bringing /DTACK low for a memory request. The 68000 has an asynchronous memory interface which means that it waits to complete a bus cycle until something tells it that the operation is complete. If /DTACK never goes low, the bus cycle lasts forever.

Thanks it's exactly what i want to know

An computer built around 68000 CPU would have a counter and logic circuit to trigger an BUS ERROR exception using the /BERR (Bus Error) pin on the CPU after a set number of machine cycles without /DTACK pulse. MD doesn't have that because was built with cost saving in mind.