IEC 62056-42:2002 pdf download

IEC 62056-42:2002 pdf download.Electricity metering – Data exchange for meter reading, tariff and load control
1 Scope
This part of IEC 62056 specifies the physical layer services and protocols within the Companion Specification for Energy Metering (COSEM) three-layer connection oriented profile for asynchronous data communication. The document does not specify physical layer signals and mechanical aspects. Local, implementation-specific issues are also not specified. In annex A, an example of how this physical layer can be used for data exchange through the Public Switched Telephone Network (PSTN) using intelligent Hayes modems is given. The use of the physical layer for the purposes of direct local data exchange using an optical port or a current loop physical interface is specified in IEC 62056-21 . Annex B gives an explanation of the role of data models and protocols in electricity meter data exchange.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60050-300:2001 , International Electrotechnical Vocabulary – Electrical and electronic measurements and measuring instruments – Part 311: General terms relating to measurements – Part 312: General terms relating to electrical measurements – Part 313: Types of electrical measuring instruments – Part 314: Specific terms according to the type of instrument IEC/TR 62051 :1 999, Electricity metering – Glossary of terms IEC 62056-21 , Electricity metering – Data exchange for meter reading, tariff and load control – Part 21: Direct local data exchange 1 IEC 62056-46, Electricity metering – Data exchange for meter reading, tariff and load control – Part 46: Data link layer using HDLC protocol 1 IEC 62056-53, Electricity metering – Data exchange for meter reading, tariff and load control – Part 53: COSEM application layer
4 Overview
From the external point of view, the physical layer provides the interface between the DTE and  From the physical connection point of view, all communications involve two sets of equipment represented by the terms caller system and called system. The caller is the system that decides to initiate a communication with a remote system known as the called party; these denominations remain valid throughout the duration of the communication. A communication is broken down into a certain number of transactions. Each transaction is represented by a transmission from the transmitter to the receiver. During the sequence of transactions, the caller and called systems take turns to act as transmitter and receiver. From the data link point of view the central station normally acts as a master, taking the initiative and controlling the data flow. The tariff device is the slave, responding to the master station. From the application point of view the central station normally acts as a client asking for services, and the tariff device acts as a server delivering the requested services. The situation involving a caller client and a called server is undoubtedly the most frequent case, but a communication based on a caller server and a called client is also possible, in particular to report the occurrence of an urgent alarm.For the purpose of local data exchange, two DTEs can be directly connected using appropriate connections. To allow using a wide variety of media, this standard does not specify the physical layer signals and their characteristics. However, the following assumptions are made: • the communication is point to point or point to multipoint; • both half-duplex and duplex connections are possible; • asynchronous transmission with 1 start bit, 8 data bits, no parity and 1 stop bit (8N1 ). From the internal point of view, the physical layer is the lowest layer in the protocol stack.