IEC 61804-3-2020 pdf free.Devices and integration in enterprise systems – Function blocks (FB) for process control and electronic device description language (EDDL)-Part 3: EDDL syntax and semantics.
The REPLY attribute contains a list of data items，which are received from the device. Theorder of the list of data items shall be maintained in the corresponding data field in thecommunicated PDU. If the referenced data items are not of type VARIABLE, the referenceddata inside the EDD elements shall always terminate as references of VARIABLE.All otherreferenced EDD element types are not allowed. The combination of LIST,VALUE_ARRAY,REFERENCE_ARRAY, and coLLECTION with an item-mask is not allowed.
When a data item does not begin and end on octet boundaries, a item-mask should be used to specify how the variable is extracted from the data field.Even if the least significant bit is not used for actual data, it should be set in an item-mask(associated with a “dummy” data item) if data items follow.
When a complete LIST instance is referenced, the EDD application shall reset the LIST and after that it shall fill the LIST with the data of the received PDU.
A variable may be qualified with both INDEX and lNFO, in which case it is called a local indexvariable.Commands with local indices behave exactly the same as commands with INDEXqualified variables except that the index variables are not stored in the device or EDDapplication.
INFO may be used to send or read a VARIABLE with units differing from those used in thedevice.
The REQUEST attribute contains a list of data items，which are sent to the device.The orderof the list of data items shall be maintained in the corresponding data field in thecommunicated PDU. lf the referenced data items are not of type VARIABLE, the referenceddata inside the EDD elements shall always terminate as references of VARIABLE.All otherreferenced EDD element types are not allowed. The combination of LIST,VALUE_ARRAY,REFERENCE_ARRAY, and coLLECTION with an item-mask is not allowed.
When a data item does not begin and end on octet boundaries of the PDU, an item-mask shallbe used to specify how the data item is packed into the data field.
Even if the least significant bit is not used for actual data it should be set in an item-mask(associated with a “dummy” data item) if data items follow.IEC 61804-3 pdf download.