I am using 7805 with the 89c51 to transfer data serially to PC the problem is that while the power is ON no data is displayed on the PC as soon as the I switch of the power a burst of DATA is displayed OR if the switch is made to ON and OFF several times then it becomes OK and start sending data continiously. I think that it is the problem with 7805 as I had connected Two 7805 with the single supply one for 89c51 and other for some other circuits
can any one know how to solve the problem.
When you see no data on the PC, is the 89C51 outputting anything at all, or is it dead? Check with an oscilloscope.
If it is sending data but nothing appears on the PC, what software is displaying the data? Maybe the data is corrupt, so the PC software displays nothing. Try viewing the data with a dumb-terminal utility such as Windows Hyper Terminal. Also try plugging and unplugging the serial cable a few times to see if the data suddenly starts working. That would be caused by what I call "false start bit syndrome".
It is very unlikely your problem is related to the 7805 voltage regulator ..
If, as you said, occasionally you have correct string on the PC's screen, try this:
Connect a switch to the reset pin of the 89C51 (of course you should have a cap there) and +5V, turn the power on, wait a couple of seconds and manually reset the micro ..
What do you have now?
if it can continously sent character 'A' to HyperTerminal, its mean your hardware configuration is OK, else recheck your program and/or HyperTerminal setup
Hi, Problem ia absolutly not with 7805, may be with ur code. Put a small delay for power-up approx:100ms at the beginning of the code. Which transformer are u using?