Tip from Product Support: Reading & Writing Data in Ethernet-based I/O with PAC Display
Our legacy serial-based FactoryFloor HMI, OptoDisplay, could access I/O data only through the controller. One of the advantages of an Ethernet-based system is that our newer PAC Project HMI, PAC Display, can access data directly from the distributed SNAP PAC brains and I/O.
Accessing data directly reduces the load on the controller and improves scanning throughput and efficiency. In fact, PAC Display is set up by default to access I/O tags directly from brains and I/O. That's what you want it to do—unless you're using the second Ethernet interface on the controller to segment your I/O network.
Dual Ethernet Interface Considerations Remember that the two Ethernet interfaces on your SNAP PAC controller are independent: they have separate IP addresses and are required to be on separate subnets.
If the PC running PAC Display is on ENET 1 and the I/O is all on ENET 2, PAC Display can't access the data directly. (By the way, if PAC Display is configured to scan through OptoOPCServer, it's the PC running OptoOPCServer that needs to be on the I/O network.) You can solve this problem in either of two ways:
If the PC with PAC Display (or OptoOPCServer) can be on the I/O network—ENET 2 in this example—either move it there or add a second NIC (network interface card) to the PC and put the second NIC on the I/O network.
If the PC with PAC Display (or OptoOPCServer) needs to be separate from the I/O network, configure PAC Display to access all I/O data through the controller, just as it would on a serial network.
If you're using SNAP PAC SB serial brains, of course data from them is accessed through the controller, too.
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