Serial Communication configures

[venkat]

In my project i'm using PIC18F4520 controller.In this project i'm using an keypad which connected with TX and RX pins.
Now i'm going to use these pins for communication also.

Shall I connect the keypad along with communication.?
When the program is started,shall we change the pin config for communication purpose only..?
During operation time(when the communication is started),we wont use keypad.

Is this is correct..?shall we use like this..?

The circuit will be like this...
The COM connector is used for communication.

[AussieSusan]

I suspect you are asking for trouble doing this. The pins you are using would appear to be for the UART which makes sense for the 'comms' part of your requirement. However, how does the keypad use these pins - does it contain a UART as well or are you just checking for some connection between these pins?
If you are using the UART, then remember that it will be driving the TX line all of the time the module is enabled; similarly it will be monitoring the RX line at the same times.
Similarly, if the 'COM' connector has an active UART on it then it will be driving its Tx line (your Rx line) and so interfere with whatever the keyboard is doing.
What are the values of the pull-up resistors on the lines? They may well interfere with the signals being passed to and from the UART.
Susan

[ric]

Also, the "COM" connector should also have a ground pin!