Re: DMA successes with Verilog

On 15/06/2018 02:06, Mia Magnusson wrote:
>> Completely off topic, can other hardware connected to the NMI line
>> drive it high when pulled low by the CIA chip without damaging the
>> chips connected to that open drain circuit. (I'm mostly a digital guy
>> and suck at analog electronics)
>> If it was possible though freezer cartridges might have utilized this.
> It's a bad thing to drive things that way. You'd drive it out of the
> spec for what the CIA can handle.

The Expert Cartridge ESM button was introduced to allow freezing of 
programs when the nmi was blocked, it has an led that lights up when an 
nmi is triggered & you know you have to press the button rather than hit 
restore (it also looks cool pulsing in time to samples).

But still after all this time it hasn't been reverse engineered or 
explained in detail, including whether it's safe.