1. It is understood that you are using the following TTL/RS232 Module (Fig-1) for inter-arduino communication.
Figure-1:
2. The above Module-1 (Fig-3) accepts TTL signal from Arduino-1 and produces RS232 signal at the female DB-9 connector side. Connect TTL side (RXD, TXD, VCC, GND) of Module-1 with Arduino-1 (Fig-3).
3. Make setup as per Fig-2.
Figure-2:
4. Upload your sketches on both Arduinos and check that data exchnage takes place correctly. Use Software UART (SUART) Port for Communication.