Connecting multiple HMI Silver Series using the Ethernet Port
Technical Note 1088
Applicable Model(s)
HMI500 Series
Title
Connecting multiple HMI Silver Series using the Ethernet Port
Date
10/22/2004
Rev
00
P/N
0907-1088
Summary
The new HMI500 “Silver Series” is a new generation of touch screens that contain a new and faster processor. The new Silver Series are now equipped with Ethernet ports (except for the HMI520M). One, or several HMIs can be connected to a PLC that uses the Modbus TCP/IP protocol. A single HMI may be directly connected to the PLC Ethernet port via a crossover Ethernet cable, or multiple Master HMIs may be connected to a PLC using an Ethernet switch and standard Ethernet cabling. Each slave HMI can communicate through the master HMI to get data from the Master HMI local memory and the PLC. No additional communications modules (other than possible network infrastructure such as routers, hubs, & switches) are required which provides an effective and inexpensive way to connect multiple HMIs to a single PLC.
The PLC must use a “Modbus TCP/IP” protocol driver if it is to be connected to the HMI Ethernet port. PLCs that use other protocols such as “Industrial Ethernet” or “AB Ethernet IP” are not supported by the HMI500 touch screens; only Modbus TCP/IP is supported.
Solution
Hardware Connection
There are several wiring scenarios for connecting HMI touch screens to a PLC. Most depend on your needs. The simplest connection (with example network IP addresses) is in a point to point connection like below:
This allows one HMI touch screen to be the master and the PLC to act as the slave device. Only one PLC can be addressed in this type of configuration.
Multiple PLCs
If more than one PLC is to be addressed by a single HMI, use the HMI RS485 port and use the “Modbus RTU Extend V3” protocol. One Slave HMI may be connected to the master via a crossover Ethernet cable or several Slave HMIs may be connected to the master using a Ethernet switch or hub device. If a hub is used, use standard Ethernet cabling and connect the HMI Master cable into the “UPLINK” port.
To configure the scenario above, select “Modbus RTU Extend V3” for the PLC type. PLC I/F should be “RS485 default”. Select Multiple HMI (Master/Slave) and connect “Ethernet”. Under the {Editor} tab of the system parameters, select “Address Mode: Extended”.
Multiple HMI Masters
If several HMIs need to be connected to one PLC and the HMIs need to be independent of one another (each can be disconnected without interrupting the other), then they can be connected as individual master devices using an Ethernet Switch as illustrated below:
This configuration can only support one PLC and all Master HMIs must use the same protocol and same server address for the PLC. A master HMI will not be able to see local memory or status of any other Master HMI. A Slave HMI can be connected to monitor/control a specific HMI Master. A slave can control & view the internal memory & status of a Master HMI.
If a router is to be used for connecting to a different network, then enter the Router IP Address and configure the router to address the PLC on its network. See the illustration below:
NOTE: The maximum distance between Ethernet cable connections is 100 meters.
Software Configuration
In the Edit >> System Parameters >> PLC tab, configure as follows:
You must configure the HMI that connects to the PLC as the master. All other HMIs should be configured as slave HMIs, unless an Ethernet switch is used, in which case the HMIs may all be masters with separate Local IP addresses and all have the same Server (PLC) IP address.
To configure Master HMIs to talk with a PLC over the Ethernet port:
1.
Click on Edit >> System Parameters and select the PLC tab.
2.
Select PLC Type: as “Modbus RTU TCP/IP”
3.
Select PLC I/F port: as “Ethernet”
4.
For the Multiple HMI box, select “Disable” if there is no slave HMIs. Select Master if any HMI is to be a slave unit and if so, select “Ethernet” for the Connect I/F.
5.
Select a unique IP Address in the Local IP Address: boxes
6.
Enter in the IP Address for the PLC in the Server IP Address: boxes. Note: Whatever the network addresses are, the numbers (Octets) in the first three boxes must match for the Local IP and the Server IP.
7.
Enter 255.255.255.0 for the Subnet Mask.
8.
If there is a router that will be between the HMI and the PLC, enter the router IP address in the “Default Route IP address”.
If there is a Ethernet connected Slave HMI unit:
To configure the Slave HMI
1.
Click on Edit >> System Parameters and select the PLC tab.
2.
Select PLC Type: as “Modbus RTU TCP/IP”
3.
Select PLC I/F port: as “Ethernet”
4.
For the Multiple HMI box, select “Enable”.
5.
Select Slave from the Multiple HMI box.
6.
Select “Ethernet” for the Connect I/F.
7.
Select a unique station number in the HMI station no. box for each slave HMI and click OK.
Sharing Data between the Master HMI, Slave HMI & PLC
Master HMI to a PLC
The master HMI will be programmed just as if it were the only HMI connected to the PLC.
Slave HMI to a Master HMI
Any local word registers (LW) or local bits (LB) located in the master HMI can be accessed (read) and written to (write) by the slave HMIs. Do this by using the “Ms_LW” and “Ms_LB” memory registers. For example, if the master HMI is storing data in LW10, the slave HMI can access that data by using a device type: Ms_LW and device address: 10. Multiple HMI is set to Master. Connect I/F is set to: Ethernet.
Slave HMI to the PLC
The slave HMI’s may access data in the PLC in 2 ways:
1.
It may write to the local words/bits in the master HMI (via Ms_LW, & Ms_LB registers) and those values may be transferred to the PLC by setting up a data transfer object in the master HMI program.
NOTE: If the master and the slave HMI’s are all accessing the same areas of memory in the PLC, this method is more efficient because the time required to get information from the PLC is reduced.
-OR-
2.
It may read/write directly to the PLC addresses (as though it were the only HMI connected to the PLC).
NOTE: This method may result in inconsistent Master/Slave communications. Maple Systems recommends using method #1.
More Information
For more information regarding connecting multiple HMI’s and connecting HMI’s via Ethernet, please refer to Technical notes: 1084, 1076, and 1075.