I was using Keil to program a Philips 89c51 chip last week to transmit data at 19200 bps. It was working perfectly, i got the data on the PC. I could also see the actual 0V - 5V waveforms on the TXD pin. This week I switched the chip to an Atmel 89c51 33 MHz one..using the same program but can't see thevoltages on the TXD pin. Tried putting a load resistor to ground, then I can see the voltages but the chip is now not speaking to my PC. Do I need to be doing something different..? thanks for all help..