Hi all,
Is the EXTINT level or edge triggered ? It's documented as being active low, however is it triggered constantly whilst held low, or only triggered on a high to low transition ?
Cheers.
Phill.
EXTINT behavior
Re: EXTINT behavior
EXTINT into ZX8302 is level triggered, ie. it will cause interrupts until cleared (to high level).
There was an early problem with QIMI and soft resets that didn't also do a hardware reset. The computer could lock up if you moved the mouse before PTR_GEN was reloaded.
The fact that this happened despite the EXTINT bit in ZX8302 interrupt register being cleared at the end of every level 2 vector call means that a high/low transition on EXTINT isn't needed to re-establish interrupt.
There was an early problem with QIMI and soft resets that didn't also do a hardware reset. The computer could lock up if you moved the mouse before PTR_GEN was reloaded.
The fact that this happened despite the EXTINT bit in ZX8302 interrupt register being cleared at the end of every level 2 vector call means that a high/low transition on EXTINT isn't needed to re-establish interrupt.
David
Re: EXTINT behavior
It's level triggered, and it's down to the interrupting device to provide some sort of interrupt acknowledge method which then returns the EXTINT line back high - such as reading or writing some hardware register etc.