//test if Process image exists
if (ModbusCoupler.getReference().getProcessImage() == null) {
response =
request.createExceptionResponse(Modbus.ILLEGAL_FUNCTION_EXCEPTION);
} else {
response = request.createResponse();
}
/*DEBUG*/
if (Modbus.debug) System.out.println("Request:" + request.getHexMessage());
if (Modbus.debug) System.out.println("Response:" + response.getHexMessage());