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.
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 influence some of the optional protocol parameters. The following line parameters can be set:
Table 1
| Parameter | Meaning | Unit | Default value |
|---|---|---|---|
Link Address | Communication line address (1 byte). | - | 1 |
| Communication Error Timeout | Timeout 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. | ms | 10 sec |
Communication station configuration
- Communication protocol: Terminal LFC (IEC870-5).
- The 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 influence some of the optional protocol parameters. The following station parameters can be set:
Table 2
| Parameter | Meaning | Unit | Default value |
|---|---|---|---|
Retry Count | Maximum count of request retries. If no response returns after a request had been sent, the station's status will change to a communication error. | - | 2 |
Retry Timeout | Timeout before resending a request if no response has been received. | ms | 100 ms |
Wait First Timeout | The delay after sending the request and before reading the response. | ms | 100 ms |
Wait Timeout | The delay between the response readings. | ms | 500 ms |
Max. Wait Retry | The maximum number of retries of the response reading. | - | 6 |
No Data Timeout | A delay after the response without any data has come (Positive Confirmation). | ms | 300 ms |
Analog Constant | A constant to calculate addresses of measurements. | - | 129 |
Analog Offset | A constant to calculate addresses of measurements. | - | 40000 |
Digital Constant | A constant to calculate addresses of the signals. | - | 501 |
Counter Constant | A constant to calculate addresses of the signals. | - | 1026 |
Counter Offset | A constant to calculate addresses of the counters. | - | 60000 |
DataClass Req. Compatibility | Compatibility of data class 1 and class 2 requests according to IEC870-5-101 specification. A value NO means that only "class 1 data" are requested. | YES/NO | NO |
Send PostMortemData | Permission to send the received data with a timestamp as so-called post-mortem data (only to an archive). | YES/NO | YES |
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 parameters 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 (measurements):
Address = ((Object - 1) * ACONST) + Value + AOFFSET - The calculation of complete address for Di, Dout tags (signals):
Address = ((Object - 1) * DCONST) + Value - The calculation of complete address for Ci tag (counters):
Address = ((Object - 1) * CCONST) + Value + COFFSET
As regards Dout tags, you can set Value address (i.e. Object and Value). Basic address data is required in 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:
- An alternate highest bit RES of Control Field is used to signalize data receiving from an active server (RES=0) in a redundant system. Otherwise, data come from a passive server and they are ignored (RES=1).
- The 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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