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EN_User_documentation_Instructions_for_controlling_the_Logamatic_5000_controller_series_via_Modbus_TCP_I
P_20210203.docx | 10.02.2021
4.
General information about Modbus TCP/IP Heart
Beat
The communication is monitored via the heart beat by means of a counter. If the
counter is not changed by the communication partner (in this case the BMS) within a
certain period of time, the control system detects a break in communication. In this
case, the error message "Connection to building control system disturbed" is dis-
played in the menu "Overview of error messages".
In the following two variants are described to realize the Modbus TCP/IP communi-
cation:
Variant 1: With Heart Beat
If you operate the "Modbus communication" parameter with the "with heart beat"
setting, the BMS must monitor the communication via a counter. For this purpose,
the BMS must write to the Modbus register "Heart Beat (in)" of the controller. As
soon as this register is written to, the timeout of the heart beat is reset. The timeout
can be set via the HMI of the controller.
The current Heart Beat value can be read, validated accordingly and incremented
via the "Heart Beat (out)" register. The "Heart Beat (out)" register always reflects the
current value from the "Heart Beat (in)" register. The validation can therefore check
whether the numerical value sent to the "Heart Beat (in)" register has been adopted
accordingly in the "Heart Beat (out)" register and use the value to increment the
counter. The value in the "Heart Beat (in)" register should be reset in time before the
overflow.
Variant 2: Without Heart Beat
If you do not have the possibility to implement the heartbeat on the BMS side, you
can also use the "no heartbeat" setting. In this case, the controller assumes that the
connection to the BMS is continuous. In this case, the detection of a communication
interruption is not available.
