> I dunno if anyone's thought of this before, but over Xmas I came up with a > nifty way of using the break button safely. With a program sitting over > the ROM in section A, I was using the following code to return basic: > > ORG 62h > back OUT (251),A ; Ensure XMEM bit is disabled > OUT (250),A ; Page ROM into section A. > nmi LD A,31 > JR back
There's no problem with NMIs when the ROM is paged out - but the problem is to trap them properly and safely when it's paged in. So in your own progs, it's easy to get the NMI to do whatever you want it to but you need a h/w hack to get NMI working properly in BASIC. The Messenger had a new NMI button on it, which worked well, but that's hardly a reason to buy one! Nige
