Maple Systems Silver HMI504T, Installation And Operation Manual

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If the slave OITs and the master OIT are both accessing the same areas of memory in the PLC, it becomes more
efficient to program the master OIT to access the PLC memory than create a Data Transfer Object to copy the PLC
data to LW and LB registers inside the master OIT. The slave OITs can then access the PLC data by using the
Ms_LW and Ms_LB registers. The biggest bottleneck in communications is trying to get all of the needed data
from the PLC. By doing this, you greatly reduce the amount of time required to get the information from the PLC.
Connecting Multiple OITs Using the Ethernet Port
The Silver Series Enhanced OITs are equipped with Ethernet ports. One, or several OITs can be connected to a
PLC that uses the Modbus TCP/IP protocol. A single OIT may be directly connected to the PLC Ethernet port via a
crossover Ethernet cable, or multiple Master OITs may be connected to a PLC using an Ethernet switch and
standard Ethernet cabling. Each slave OIT can communicate through the master OIT to get data from Master OIT
local memory and the PLC. No additional communications modules (other than possible network infrastructure
such as routers, hubs and switches) are required, providing an effective an inexpensive way to connect multiple
OITs to a single PLC.
The PLC must use a Modbus TCP/IP protocol driver if it is to be connected to the OIT Ethernet port. Support for
other Ethernet protocol drivers are available in our Silver Series Plus products. Please consult our website for more
information on these products.
Hard ware Con nec tions
There are several wiring scenarios for connecting OIT touchscreens to a PLC. Most depend upon individual needs.
The simplest connection (with example network IP addresses) is a point-to-point connection, such as the one
illustrated below:
This allows one OIT touchscreen 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 OIT Masters
If several OITs need to be connected to one PLC and the OITs need to be independent of one another (each can be
1010-1001a, Rev 02
72 Sil ver Se ries In stal la tion & Op er a tion Man ual
Ethernet Crossover
OIT
(Master)
PLC
192.168.0.50
L:192.168.0.10
S:192.168.0.50
Sub:255.255.255.0