Using The Vmse On An Rs-422/485 Multidrop Network; Multidrop Application Notes - GE VersaMax IC200SET001 User Manual

6

Using the VMSE on an RS-422/485 Multidrop Network

The following figure shows an acceptable configuration for a multidrop
network. This example shows only two slave devices; if additional slaves
were added, termination would be required at the last slave device instead of at
Slave #2.
Master
Serial
Line 1
*
**
Figure 6-14. Using the VMSE in a Multidrop Arrangement

Multidrop Application Notes

•
Any serial line longer than 6 feet (2 meters) must have a termination
resistor across its receive terminals (RD or RX) at the end of each receive
line.
•
The serial port on the VMSE #2 screw terminals must be used since it is
the only VMSE port that supports RS-422. The VMSE's RJ-45 Serial
port cannot be used since it is an RS-232 port only, and RS-232 does not
support multidrop.
•
The switch on the front of the VMSE #2 must be set to RS-422 position to
enable RS-422 on the VMSE screw terminals. Also, the "Interface Type"
configuration parameter must be set to RS-422 (no other setting is
acceptable).
•
Serial Line 1 may be RS-232 or RS-422 as long as both Master and
VMSE #1 are configured accordingly.
•
For Serial Line 2, which must be an RS-422 line, match the specifications
and basic wiring scheme for User-Built Cable #4. All multidrop
connections must be made at the nodes inside the connectors (thus, each
connector terminal would have two wires attached), in a parallel "daisy-
chain" style. No line stubs or intermediate terminal blocks are permitted.
•
Each serial cable's shield must be grounded at one end of the cable only.
•
The VMSE can be the only device connected to the master on Serial Line
1 shown in Figure 6-14 above.
6-10 VersaMax Serial to Ethernet Adapter User Manual
Switch=**
VMSE #1
Ethernet Cable
Termination is required across RD or RX terminals at these locations if the serial
line is greater than 6 feet (2 meters) long
VMSE #1 must be set to the configuration (RS-232 or RS-422) that matches the Master
Slave
#1
Switch=RS-422
*
VMSE #2
Slave
#2
*
Serial
Line 2
GFK-1852B