We are using the processor's internal ROM (EA=1) and the first 256 bytes of internal RAM. Looking at the AUXR (8E) register, the default should be to use external RAM for xdata variables i.e. loaded with 0x0B at startup - so we discarded this possiblity. The address lines are held low and no addressing occurs at all. The processor starts up, because ports 1 and 3 are responding, but fails to do any external RAM fetches. Any ideas???