stack overflow executing call instruction in 16f877a

Friends, i am doing a micro controller project to control the water level of 3 different water tanks.
Hence, i planned to use 2 sensors for each water tank. One to indicate LOW water level and another one sensor to indicate HIGH water level in each tank.

I planned to do this in 16f877a.

For that, i have assigned this instructions.

1. I made first 6 pins of PORT B as input and registered RBPU=1 in order to clear the pull up resistance.

2. Also, i made 7th pin of PORT B and 7th and 8th pin of PORT C as OUTPUT PINS.

3. There is no sensors available in PROTEUS. so i assumed that a 5 volt can be added as a sensor(just for consideration).

4. I have just given all the connections.

5. I assumed that 2nd, 4th and 6th pins of PORT B are pins getting LOW signal from 3 tanks.

6. I switched on the PUSH buttons which are connected at 2nd, 4th and 6th pins of PORT B.

7. After doing this, i am getting the warning tat "STACK OVERFLOW EXECUTING CALL FUNCTION.




Do you have any idea about the following error.?


I have attached all the files which are being used in this program.

Please suggest me a solution to solve the above warning. :smile:

Thanks in ADVANCE.