16f877a usart subtleties

hi mel and gang, just finally punching through a bunch of code to get two usarts chatting together without using pbp's functions. Everything is done through the 16f877a's registers.
The question is...... why would i have to tie down (10k) the transmission line to get a good reception. I didn't see any indication in any of the manuals that the port had to be tied at all to enable the usarts functions. Is it more a problem of noise and the tiedown is a bandaid solution.
Or is a 10k tie down something that everyone has found to be the best manner to make these pics work.....garret

The main question is... Are all those PIC on the same board? If not, what is the distance between them.

Using a pair of MAX232 is a common choice. Some will use a pair of opto-isolator, schmitt trigger, buffer op-amp or direct drive.

We can't help since every projects are different and you didn't provide much infos.

BUT using 10K resistor or lower can be a solution to avoid 'some' noise