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Terminal LFC (IEC 870-5) communication protocol

Supported device types and versions
Communication line configuration
Communication line protocol parameters
Communication station configuration
Communication station parameters
I/O tag configuration
Literature
Changes and modifications
Document revisions

Supported device types and versions


This communication supports data reading and writing by IEC870-5-101 communication protocol with special modifications. TCP/IP UDP network communication or a serial communication on Serial or SerialOverUDP Device Redundant communication line can be used.

An implementation according to IEC870-5-101 standard:

  • Originator ASDU address - omitted.
  • ASDU address - it is 1 byte and represents a station address. A different ASDU address of each station on the same line is required.
  • Cause of transmission - it is 1 byte (it does not contain Originator ASDU address).
  • Information object address - 2 bytes, it represents I/O tag address.


Communication line configuration


  • Communication line category: Serial, TCP/IP-UDP, SerialOverUDP Device Redundant
  • UDP Parameters:
    • The parameters of primary server or secondary one are required.
    • Host: string max. 80 characters – a server name in the INET form (the name or numerical address a.b.c.d).
    • Port: UDP port number (1 to 65535).

Communication line protocol parameters


Configuration line dialog box - tab Protocol parameters.
They influences some of the optional protocol parameters. The following line parameters can be set:

Table 1

ParameterMeaningUnitDefault value
Link AddressCommunication line address (1 byte).-1
Communication Error TimeoutTimeout defined for the check of communication on the line (or on the lines of primary or backup communication in case of UDP communication). If communication does not work longer than it is this value, the values of all communication stations on the line will be transferred to StCOMERR state.ms10 sec

Communication station configuration


  • Communication protocol: Terminal LFC (IEC870-5).
  • Station address is a decimal number ranging from 0 up to 255. It represents the ASDU address in the protocol.

Communication station parameters


Configuration station dialog box - tab Protocol parameters.
They influences some of the optional protocol parameters. The following station parameters can be set:

Table 2

ParameterMeaningUnitDefault value
Retry CountNumber of the call retry when some communication error occurs.-2
Retry TimeoutA delay between the call retries when some communication error occurs.ms100 ms
Wait First TimeoutTime of the first waiting for response after the call has been sent.ms100 ms
Wait TimeoutA delay between reading of the response till its completing.ms500 ms
Max. Wait RetryNumber of retry of response reading till its completing.-6
No Data TimeoutA delay after the response without data has come (Positive Quittung).ms300 ms
Analog ConstantA constant to calculate an address of a measurement.-129
Analog OffsetA constant to calculate an address of a measurement.-40000
Digital ConstantA constant to calculate an address of the signals.-501
Counter ConstantA constant to calculate an address of the signals.-1026
Counter OffsetA constant to calculate an address of the counters.-60000
DataClass Req. CompatibilityA compatibility of data class 1 and class 2 requests according to IEC870-5-101 specification. A value NO means that only data class 1 are called.YES/NONO
Send PostMortemDataPermission to send a received data with a timestamp as so-called post-mortem data (only to an archive).YES/NOYES

I/O tag configuration


A possible I/O tags: Ai, Ao, Ci, Di, Dout, Qi

The address consists of two parameters - Object and Value.

These parameter are used to calculate the address (in the range 0 to 65535) according to these formulas:

  • The calculation of complete address for Ai, Ao tags (the measurements):

    Address = ((Object - 1) * ACONST) + Value + AOFFSET
  • The calculation of complete address for Di, Dout tags (the signals):

    Address = ((Object - 1) * DCONST) + Value


  • The calculation of complete address for Ci tag (the counters):

    Address = ((Object - 1) * CCONST) + Value + COFFSET

As regards Dout tags, you can set Value address (i.e. Object and Value). A basic address data is required at writing. Value address is used to update I/O tag value at reading.

Specific differences between IEC870-5 and IEC870-5-101 protocols


The differences between IEC870-5 and IEC870-5-101 protocols:

  1. An alternate highest bit RES of Control Field is used which signalized data receiving from an active server (RES=0). Otherwise, data are ignored (RES=1).
  2. An arrival of the binary value TRUE to the object with address 65007 (so-called USAN bit) signalized a transition of I/O tag values of all stations to the value with "Weak" flag, i.e. all values become invalid.

Literature


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Changes and modifications


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Document revisions


  • Ver. 1.0 – February 9th, 2000.
  • Ver. 1.1 – July 11th, 2003 - scan mode.
  • Ver. 1.2 - January 25th, 2011 - document update.


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