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4. The Function of Serial Port Connectors
Port3 Connector:
The signal level of Port3 connector is of RS232(CM25E) or
RS485(CM55E). This port can be treated as a general communication port
of CPU module and used for peripheral applications.
Port4 Connector:
The signal level of Port4 connector is of RS485(CM55E). The main
function of this port is to couple the Ethernet signal to CPU module, this
port also can be treated as a general communication port of CPU module
and used for peripheral applications. Whenever the FBs-CMX5E module
receive a data packet from the Ethernet interface, the same data packet
also will appear at this port(Ethernet to serial port conversion). On the
contrary, if a data packet is received at this port and the destination is
due for network (by lookup mapping table), it will also appear at Ethernet
network. Because the multi-drop characteristic of RS485 interface, install
one FBs-CMX5E can provide more than one PLC to hook on Ethernet.
5. The Function of Ethernet Serial Converter
The operation principle of Ethernet serial converter is to take this module
as interface and receive all the messages from network that intend to the
PLCs managed by this module then convert it to the serial signal that can
be accepted by PLC and transmit it thru port4. The operation is
completely transparent, in other words, The CPU cannot distinguish the
message is from local or network, the reply message is the same with
normal RS232communication. When the FBs-CMX5E or FBs-CBE
module(for clarity it will be referred as Ethernet module in following
context) receives the reply message of PLC will pack the message into
network data packet then send it to the network. It must emphasis here
that the network environment is complicated and not adequate for real
time data transfer and can be use mainly for monitoring but not for control.
The main reason to use the network for factory communication is for its
connectivity. The application, which required to access one processor at
same time by multiple clients, previous was difficult to implement by
RS232 and RS485 can now easily achieve by network solution.
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