On Tue, 17 Jan 1995 15:05:16 +0000 (GMT), Steve Taylor said: > I dunno if anyone's thought of this before,
Yes. See my sample player which I posted on this list some time ago... ;-) [snip] > So, I decided to alter the code to pause for a bit before returning to > basic, and junking any return addresses generated by subsequent nmis, > avoiding any stack overflow: > ORG 62h > back OUT (251),A > OUT (250),A > nmi POP HL ; junk return address > LD BC,1000h > loop DJNZ loop > DEC C > JR NZ,loop > LD A,31 > JR back The alternative which the MGT snapshotter uses is to do the delay first and then clean up the stack (it has to do it this way round in order to guarantee a safe return to the program that was interrupted). You have to press the break button very carefully in order to avoid overflowing the stack. ;-) Unfortunately, it doesn't quite know when to stop with the result that if you do something like "PRINT USR 102" from a spectrum emulator and then try to return to it, the thing crashes. I wrote a slightly better version of it once (I think it might be on the Syncytium disk). All of this would have been unnecessary if they had just spent an extra 60p and installed a proper break button... imc
