Overview
IEC 62056-42:2002 is an International Electrotechnical Commission standard that specifies the physical layer services and procedures for the COSEM (COmpanion Specification for Energy Metering) three‑layer connection‑oriented profile used in electricity metering data exchange. The standard defines service primitives and the physical‑layer protocol behavior for asynchronous, connection‑oriented communications between Data Terminal Equipment (DTE) and Data Communication Equipment (DCE). It does not define electrical signals or mechanical interfaces, but describes how the physical layer interacts with higher COSEM layers and gives practical examples (Annex A: PSTN with Hayes modems; Annex B: role of data models and protocols).
Keywords: IEC 62056-42, COSEM, physical layer, electricity metering, asynchronous data exchange, meter reading.
Key topics and technical requirements
- Scope and purpose: Defines services and protocol procedures for the physical layer in the COSEM three‑layer connection‑oriented profile used for meter reading, tariff and load control.
- Service primitives: Specifies standard service primitives used by the physical layer, including:
- Connection management: PH-CONNECT.request / PH-CONNECT.indication / PH-CONNECT.confirm
- Abort/disconnect: PH-ABORT.request / PH-ABORT.confirm / PH-ABORT.indication
- Data transfer: PH-DATA.request / PH-DATA.indication
- Additional layer management primitives are noted (e.g., PH-INITIALIZE, PH-GET_VALUE) but are implementation‑specific.
- Protocol behavior: Defines transmission order, PH‑PDU and PHSDU concepts, identification service and procedures for setting up, using and tearing down physical connections.
- Assumptions: For broad media support the standard assumes point‑to‑point or point‑to‑multipoint operation, half‑duplex and full‑duplex capability, and common asynchronous framing (notably 8N1 is referenced as typical).
- Examples and guidance: Annex A illustrates use over PSTN with intelligent Hayes modems; Annex B explains the relationship between COSEM data models and protocols.
Keywords: PH-CONNECT, PH-DATA, PH-ABORT, PSTN, Hayes modems, PHSDU.
Applications and who uses it
- Meter manufacturers implement the physical‑layer services in meter communications modules to ensure interoperable remote reading and control.
- Utilities and metering service providers rely on compliant devices for automated meter reading (AMR), tariff updates and remote load control.
- Modem and DCE vendors use Annex A guidance to support modem command sequences and PSTN operation with COSEM devices.
- System integrators and software developers implement the COSEM protocol stack (physical → data link → application) and test service primitives and state machines.
- Test labs and compliance bodies verify conformance to the service primitives and connection procedures defined by the standard.
Keywords: automated meter reading, AMR, metering communications, meter interoperability.
Related standards
- IEC 62056-21 (local direct data exchange)
- IEC 62056-46 (data link layer - HDLC)
- IEC 62056-53 (COSEM application layer)
- IEC 62056-61 / -62 (OBIS and interface objects)
- NEMA C12.21 (telephone modem protocol)
Using IEC 62056-42 ensures consistent physical‑layer behavior within COSEM‑based metering solutions and supports interoperable electricity metering communications across vendors and networks.