DIN EN 62056-21 : 2003

INTRODUCTION
1 Scope
2 Normative references
3 Terms, definitions and abbreviations
  3.1 Terms and definitions
  3.2 Abbreviations
4 Physical properties
  4.1 Electrical current loop interface
  4.2 Electrical interface V.24/V.28
  4.3 Optical interface
      4.3.1 Construction of the reading head
      4.3.2 Characteristic data of the magnet
      4.3.3 Arrangement of components in the tariff device
      4.3.4 Alignment
      4.3.5 Optical characteristics
5 Character transmission
  5.1 Type of transmission
  5.2 Transmission speed
  5.3 Signal quality
  5.4 Character format
  5.5 Character code
  5.6 Character security
6 Data transmission protocol
  6.1 General
  6.2 Calculation of the block check character
  6.3 Message definitions
      6.3.1 Request message
      6.3.2 Identification message
      6.3.3 Acknowledgement/option select message
      6.3.4 Data message (except in programming mode)
      6.3.5 Acknowledgement message
      6.3.6 Repeat-request message
      6.3.7 Programming command message
      6.3.8 Programming command message using optional partial
             blocks
      6.3.9 Data message (programming mode)
      6.3.10 Data message (programming mode) using optional partial
             blocks
      6.3.11 Error message (programming mode)
      6.3.12 Break message (programming mode)
      6.3.13 Block message (other protocols)
      6.3.14 Explanations of message contents
  6.4 Communication modes
      6.4.1 Protocol mode A
      6.4.2 Protocol mode B
      6.4.3 Protocol mode C
      6.4.4 Protocol mode D
      6.4.5 Protocol mode E (other protocols)
      6.4.6 Entering programming mode (unknown tariff device)
      6.4.7 Partial block communication (optional, only in protocol
            mode C)
  6.5 Syntax diagrams
      6.5.1 Readout mode
      6.5.2 Programming mode
  6.6 Data set structure
Annex A (normative) Flow chart for direct local data exchange
        protocol, protocol mode C
Annex B (normative) Wake-up methods for battery-operated tariff
        devices
Annex C (informative) Formatted codes
Annex D (informative) Levels of access - system security
Annex E (normative) METERING HDLC protocol using protocol mode E
        for direct local data exchange
Annex ZA (normative) Normative references to international
         publications with their corresponding European
         publications
Bibliography
Index

Specifies hardware and protocol specifications for local meter data exchange. In such systems, a hand- held unit (HHU) or a unit with equivalent functions is connected to a tariff device or a group of devices.