Hello Richard,

You are not handling IE0 correctly. Set it to 0 in your initialization function (IE0 = 0;). When main starts out IE0 will go high after you enable EX0. This is due to a quirk. This should make your button behave normally. Should you want to go into external interrupt after the button is push set IE0 to 1 (IE0 = 1;). This will force an interrupt which will be serviced. You also have to clear this manually (I think).

Regards,

Charles Bannister