On Mon, 21 Mar 2005 20:47:32 +0530, Sandeepa.D.Khale wrote:

> I am trying to send characters to the PC using the hardware UART in 16f877a.
> The problem is that the characters are displayed only after I switch
> off the power to the PIC.

What terminal program are you using on the PC?  It sounds like it's buffering the data coming from the PIC and 
only displaying it when it thinks the PIC has finished sending (are you sending Carriage Return or any other 
end-of-line character?).  The fact that the characters do appear at all means that the PIC was working at one 
time...

> I have tried various snippets of codes used
> successfully by others,however the result is always the same.
> I am using MAX232 between the PC and the PIC.
> Also when I tried receiving a character and transmitting it
> again,nothing happened.i.e. even after powering down the PIC,nothing
> was displayed as was the case previously.
> Shorting the Tx and Rx pins however displays the keyed in character on
> the screen.

Which Tx & Rx pins?  If you mean the ones on the PC side of the MAX232, then all this shows is that the cable 
is connected and working - it doesn't even prove that you've got the Tx & Rx the right way round!  If you mean 
on the PIC side of the MAX232 (or on the PIC itself) then you've proved that the MAX232 is working, but if you 
did it with the PIC in place, you may have damaged its output pin circuit (because it would be fighting the 
data coming across from the other pin).

> What could be going wrong?

The list is long - we need to shorten it by eliminating some possibilities, starting with the PC software.

Cheers,


Howard Winter
St.Albans, England


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