I can't get the code to return from the EINT1 ISR with GNU, but works fine with CARM...
Take a look to: http://www.keil.com/download/docs/mcb2100_extint.zip.asp It should be fairly easy to convert this program to GNU with the info in: http://www.keil.com/support/docs/2968.htm Reinhard
I'd looked at that code previously, but the one issue I had not considered too seriously was the EXTMODE, that seems to work in such a way that it stoped the timer ISR. I'll have to look at that more closely... thanks