Connect a device CRT 711 Card Issuing/Collecting Machine to a Rabbit LP3500


I have been working to connect a device CRT-711 Card Issuing/Collectting machine to serial port C. This device use the serial port to send and receive information to handle a paper card. Use data type named byte. It means that each byte that device send/receive is an instruction to the device.
Each byte has to be sent in a chain.
Could you help me with this problem?

Thanks in advance for your help

What have you tried so far? Do you know the baud rate of the device? Is it operating at TTL or RS232 serial levels? Can you connect the CRT711 to a PC serial port and see the bytes its sending? Can you connect it to the LP3500’s serial port and use one of the sample programs to get a dump of the bytes coming in?