16f877a usart subtleties

[garret]

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

[mister_e]

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