General query and groups

The sample program presented here shows an IEC 60870-5-104 master with Low Level interface. The sample illustrates the definition of groups of data types. A general interrogation and a separate group 1 are configured. The general interrogation takes place every 30 seconds, group 1 is interrogated every 10 seconds. The communicated parameters include single points, bitstrings and measured values.

In the sample, the following parameters are set for the central station (master):

• Server Host address (IP address of the slave): 127.0.0.1 (At least this parameter must be adjusted individually)
• Server port address (port address of the slave): 2404
• k: 12
• w: 8
• t0: 30 s
• t1: 15 s
• t2: 10 s
• t3: 20 s
• General ASDU address: 3
• Cause of transfer size: 2 octets
• Common ASDU address size: 2 octets
• Information object address size: 3 octets
• Max. APDU length: 253

Important notes:

We make no claim to completeness and correctness. Set the IP address of the slave, both in the master part and in the slave part! Verify that port 2404 is not blocked by a firewall!

The connection is established after the start of the program. The data points are managed in the Global Variable List (GVL).