X20 system modules • Analog input modules • X20AI2438
X20 system User's Manual 3.10
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4.3.7.9.8.2 HART - Configuration
HART modules are analog modules equipped with a HART modem. For each channel, a separate HART network
can be managed by the module, which acts as a primary master. Once configured successfully, the HART infor-
mation is stored in the module where it can then be used by the PLC.
The number of HART slaves must be specified in the configuration.
If only one slave is connected to the HART channel, then it is part of a point-to-point network. The module can then
prepare up to four process variables from the connected slave.
Multidrop mode allows up to 15 HART slaves to be connected. The primary process variable from each slave is
then retrieved.
HartNodeCnt
The "HartNodeCnt" registers tell the module how many HART slaves are connected to a channel.
Information:
If a slave is not connected to one of the HART channels, the value "0" should be defined in this register.
This shortens the I/O update time and avoids superfluous error messages.
Data type
Values
USINT
0
HART communication disabled for this channel
1
Point-to-point
Standard HART communication (bus controller default)
2 to 15
Multidrop
Number of HART slave nodes
HartBurstNode
In addition to the type of network, the user can also choose from two different types of communication behavior.
Conventional HART communication relies on polling. The module requests the data from the individual HART
slaves and receives the corresponding information from each slave as a response. If a HART node should be
queried in short time intervals, the user can configure burst mode for channels on one node. In this case, the slave
transmits the node's information cyclically without constant prompting from the master.
The "HartBurstNode" registers are therefore used to enter the node numbers (short address) for the channels
whose information should be retrieved using burst mode. Burst mode itself is enabled with the "HartMode" register.
Data type
Values
USINT
0 to 15
Point-to-point → 0 (bus controller default)
HartMode
The user can use the "HartMode" registers to configure the communication behavior of each of the HART channels.
Generally, the HART nodes are polled individually. This register can still be used to start or stop burst mode when
needed.
In burst mode, a node transmits its information cyclically instead of continuously. As a result, the HART standard
allows the simultaneous usage of both burst mode and polling.
Information:
To retrieve information with burst mode, the "HartBurstNode" register must be configured correctly.
Data type
Values
USINT
See bit structure
Bit structure:
Bit
Name
Information
0
Polling mode enabled (bus controller default)
0
Slave polling mode
1
Polling mode disabled
0
No response to burst (bus controller default)
1
Start slave burst mode
1
Enables burst mode in the "HartBurstNode" node
0
No response to burst (bus controller default)
2
Stop slave burst mode
1
Disables burst mode if enabled
3-7
Reserved
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