I have a comms program that definitely works OK on a Philips P89C51Rx+ but fails on a Temic T89C52RD2 - serial data simply does not get received (although transmission works fine). It appears as if the RI bit isn't getting set, so no interrupt occurs and the data gets ignored. I'm using Mode 1, and have checked that REN=1 and SM2=0.

Does anyone know of any subtle difference between Temic and Philips devices, registers, etc. that may cause such a problem?