Thanks for your responses. The PLC and the HMI are communicating serially before. The line was down due to mechanical fault. After been resolved, the machine was power on and I discovered that the data was not loading to the HMI. I also observed that the battery alarm was flashing. It was changed and the program was downloaded. The data was uploaded but when I begin to adjust some parameters, it went off again and it has never come up again. Is still pending