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..
1. Are the SFRs setup correctly? 2. If you're looking at the TXD pin there should be activity even if the baudrate is wrong. Why would you connect the load resistor to ground? IF the output is open drain you need a pull up to VDD. Happy hunting
Hey all, thanks for the help.. I'm sorry for the trbl. Somehow I was enabling interrupts without an interrupt routine. I still don't know how it worked on the philips. Thanks Anil