Association information is set from one CSPP element in the COMM_IF_CONFIGURATION part managing machine information to one or more machine data in the BLOCK_MEMORY part or BLOCK_PARAM part. This means that aggregation of more than one machine data creates one machine information. The reason why this structure is required is that the information required by application software needs not only a simple measured value (current value) but also the accompanying information such as the time when the value is measured and accuracy of the value.
In contrast, setting association information from the CSPP element in the COMM_IF_VARIABLE part as the machine information to the machine data in the BLOCK_MEMORY part or BLOCK_PARAM part is not allowed. This is because the application is for realtime monitor and all the information required in the machine information can be described. Association between the machine information and machine data is illustrated in Figure 54.