LLC逻辑链路控制-DLMS-結構解析

LLC逻辑链路控制The LLC sub-layer符合ISO 8802-2 LLC1 layer for本地网络.在DLMS的实际应用中, LLC只作了“规约选择”.所有的寻址和服务的控制由下一层的MAC层所提供-逻辑设备寻址用高位HDLC地址,物理设备用底位HDLC地址* This information is contained in a special COSEM object, the “association” object. There are two types of this association object defined. One for associations using short name referencing (“Association SN”) and one for using logical name referencing (“Association LN”). Depending on the association established between the client and the server different access rights may be granted by the server. Access rights concern a set of COSEM objects – the visible objects – that can be accessed (‘seen’) within the given association. In addition, access to attributes and methods of these COSEM objects may also be restricted within the association (e.g. a certain type of client can only read a particular attribute of a COSEM object). The list of the visible COSEM objects – the “association view” – can be obtained by the client by reading the “object_list” attribute of the appropriate association object. Additional information about the access rights (read only, write only, read and write) to the attributes and the availability of the methods (within the established association) can be found via specific attributes (Logical name referencing) or special methods (Short name referencing) provided by the association objects.