Machine Lock-up

mickagame · Post by **mickagame** » Thu Oct 16, 2014 8:57 am

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

HardWareMan · Post by **HardWareMan** » Thu Oct 16, 2014 11:52 am

Use search engine.

Post by **KanedaFr** » Thu Oct 16, 2014 12:13 pm

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

Mask of Destiny · Post by **Mask of Destiny** » Thu Oct 16, 2014 8:36 pm

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.

mickagame · Post by **mickagame** » Fri Oct 17, 2014 5:58 am

Thanks it's exactly what i want to know

l_oliveira · Post by **l_oliveira** » Tue Dec 30, 2014 5:56 am

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.