When the retained (non-volatile) internal memory of HMI is used to store history sampling and alarm data, the recorded data occupies the retained (non-volatile) internal memory of HMI. However, when the internal memory is full, the HMI programs may not compile successfully. Please refer to the following example for the method of calculating the HMI internal memory size. 1.History Setup: Step 1: Enter [Options] --> [History Setup] to set up the properties of the history data. Step 2: Click the [Add] button to add a History datum. Step 3: Set the [Buffer Properties] as below: Suppose that the data length of the history data is set to 5 (5 words = 10 Bytes) and the sample number of the history data is set to 600. The history data has the time and date recorded, so it occupies 6 Bytes for each sampling cycle. The required file capacity for the history data is: The file capacity of the history data = [(10 Bytes + 6 Bytes) × 600] = 9600 Bytes = 9.6 KB. You can also refer to the HMI Memory dialog box by clicking [View] > [Memory List] to see the memory usage and space changes as shown in the figure below. 2.Alarm Setup: Step 1: Enter [Options] --> [Alarm Setup] to set up the properties of the alarm. Step 2: Set the Read Address, Scan Time and Max. Records. The Read Address selects the internal memory or controller register address. The Scan Time indicates the interval to take a sampling action. When the records accumulate to the number shown in Max. Records, the recording starts again from the first data and overrides the previous data. Please refer to the figure below. Suppose that the alarm data length is set to 1 (1 words = 2 Bytes) and the Max. Records of the alarm data is set to 600. With the Hold box checked and the HMI option selected, it means that the alarm data is recorded to the HMI internal memory in case of an outage, so it occupies 6 Bytes for each sampling cycle. Required file capacity for the alarm data is: File capacity of the alarm data = [(2 Bytes + 6 Bytes) × 600] = 4800 Bytes = 4.8 KB. You can also refer to the HMI Memory dialog box by clicking [View] > [Memory List] to see the memory usage and space changes as shown in the figure below.