Examples of Modbus Routing

Presentation

This topic presents examples to illustrate how an upstream SCADA using Modbus TCP/IP accesses the devices connected to a Panel Server depending on the communication architecture using the Modbus virtual server ID. For detailed information about Modbus unit ID / server ID and virtual server ID, see definitions.

NOTE: Modbus routing should not be confused with network routing at the network (IP) layer.

Availability

This function is available on Panel Server Entry, Universal, and Advanced. The function is available depending on the model.

Recommendations for Virtual Server ID Mapping

To help ensure consistency of device data being communicated to upstream system, follow these rules for virtual server ID mapping:

1–99 for Modbus-SL devices (Universal and Advanced models)
100–199 for wireless devices
200–254 for Modbus TCP/IP devices (Universal and Advanced models)

Example of Modbus TCP/IP Requests for Wireless Devices

This example presents the Modbus TCP/IP requests for wireless devices.

Panel Server with IP address 10.10.11.12 is connected to:

a HeatTag configured with virtual server ID 101, and
an Acti9 Active configured with virtual server ID 102.

To collect and gather data from the wireless devices, the monitoring system will issue the following Modbus TCP/IP requests:

10.10.11.12, address 101 for HeatTag
10.10.11.12, address 102 for Acti9 Active

Example of Modbus TCP/IP Requests for Modbus-SL Devices

This example applies to Universal and Advanced models.

This example presents the Modbus TCP/IP requests for Modbus-SL devices when the serial physical address is used as virtual server ID.

Panel Server with IP address 10.10.11.12 is connected to:

an iEM3150 with physical address 1, and
an iEM3155 with physical address 2.

To collect and gather data from the Modbus RS485 devices, the monitoring system will issue the following Modbus TCP/IP requests:

10.10.11.12, address 1 for iEM3150
10.10.11.12, address 2 for iEM3155

Example of Modbus TCP/IP Requests for Modbus-SL Devices With Virtual Server ID Different from the Physical Address

This example applies to Universal and Advanced models.

A virtual server ID which is different from the physical address can be used in the following cases:

The physical address is already used as a virtual server ID for a different device (either a wireless, Modbus-SL, or Modbus TCP/IP device).
This use case helps to apply a dedicated communication address plan for easier and consistent integration in the upstream system.

This example presents the Modbus TCP/IP requests when the virtual server ID of Modbus-SL devices is different from the serial physical address.

Panel Server with IP address 10.10.11.12 and virtual server ID 15 is connected to:

an iEM3150 with physical address 100 and virtual server ID 10, and
an iEM3155 with physical address 101 and virtual server ID 15.

To collect and gather data from the Modbus devices, the monitoring system will issue the following Modbus TCP/IP requests:

10.10.11.12, address 10 for iEM3150
10.10.11.12, address 15 for iEM3155

Example of Modbus TCP/IP Requests for Devices in Separate Topology

This example applies to Universal and Advanced models.

This example presents the Modbus TCP/IP requests for devices in a separate topology.

Panel Server with

IP address on ETH1 port: 10.10.10.10
IP address on ETH2 port: 192.168.10.1

is connected to:

a PM800 with IP address 192.168.10.2 and virtual server ID 200, and
a PM5563 with IP address 192.168.10.3 and virtual server ID 201

To collect and gather data from the Ethernet devices, the monitoring system will issue the following Modbus TCP/IP requests:

10.10.10.10, address 200 for PM800
10.10.10.10, address 201 for PM5563

Modbus service is to be enabled on ETH1.

Example of Modbus TCP/IP Requests for Devices in Switched Topology

This example applies to Universal and Advanced models.

This solution offers multiple Modbus TCP client connections. If a device supports only one Modbus TCP/IP client, the Panel Server acts as a Modbus TCP/IP proxy and can support several upstream connections.

This example presents the Modbus TCP requests for devices in a switched topology.

Panel Server with IP address 10.10.10.10 is connected to:

a PM800 with IP address 10.10.10.11 and virtual server ID 200, and
a PM5563 with IP address 10.10.10.12 and virtual server ID 201.

To collect and gather data from the Ethernet devices, the monitoring system will issue the following Modbus TCP/IP requests in one of the following ways:

Requests are issued directly to the downstream device:
- 10.10.10.11, address 255 for PM800
- 10.10.10.12, address 255 for PM5563
or requests are issued through the Panel Server and the Modbus device discovery uses the virtual server ID:
- 10.10.10.10, address 200 for PM800
- 10.10.10.10, address 201 for PM5563

Example of Modbus TCP/IP Requests for Modbus-SL Devices under a Child Panel Server in Separate Topology

This example applies to Universal and Advanced models.

This example presents the Modbus TCP/IP requests for Modbus-SL devices when they are connected to a child/downstream Panel Server in a separate topology: the child/downstream Panel Server (PAS#2) is connected to one Ethernet port on the parent/upstream Panel Server (PAS#1).

For information on how to discover Modbus-SL devices connected to a child/downstream Panel Server by using Panel Server webpages, see detailed topic.

PAS#1 with

IP address on ETH1 port: 10.10.10.10
IP address on ETH2 port: 192.168.10.10

is connected to child PAS#2 with IP address 192.168.10.11 and connected to:

an iEM3150 with physical address 1, and
an iEM3155 with physical address 2.

To access the Modbus-SL devices under the child/downstream Panel Server (PAS#2) from the monitoring system, first the Modbus-SL devices must be manually added to the parent/upstream Panel Server (PAS#1) with the Panel Server webpages:

Manual addition of iEM3150 to PAS#1 is done by using 192.168.10.11, address 1, assigned to virtual server ID 200.
Manual addition of iEM3155 to PAS#1 is done by using 192.168.10.11, address 2, assigned to virtual server ID 201.

Then to collect and gather data from the Modbus devices, the monitoring system will issue the following Modbus TCP/IP requests:

10.10.10.10, address 200 for iEM3150
10.10.10.10, address 201 for iEM3155