rs485 communication using SN75176 trancievers between pic18f452

my project has two units
1- control unit.
2- ballot unit.

i have completed control unit having a pic18f452 connected with barcode scanner and sdcard and tft display.in control unit sdcard contains data of voters from which data is read and compared with the one coming from barcode scanner. and displaying on the glcd/tft that if matched can cast vote.

problem:
now the problem is i m not getting idea how can i make my control and ballot unit communicate i-e ballot unit have switches with leds. now when glcd of control unit display that voter can cast vote then voter will press switch of the desired party to be voted and control unit will recive message that vote have been casted and voter is not allowed to press multiple switches.....

can anyone please help me in my problem
i m using mikroc pro v 4.15 or 5.16 and proteus v7.8.
my control unit code and ballot unit code and schematic is attached

Do you want the code for communication using the SN75176 Tranceivers?

yes i want it

for RS485 communication between control and ballot unit i m using Sn75176 between two pic18f452

Why can't you use serial communication between the 2 PIC's? Can you post the .dsn file of the image you have posted?

.dsn file of the above image

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RS485 is a serial communication & as i needed differential communication to work so i m using this one

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can you help me in my communication work because i have never done any work on communication before and as you know just three days to show stimulation before hardware panel on proteus.