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Connecting to the Host’s RS-422A/485 Port Section 5-2
Reference: • The internal circuit of the NT631/NT631C is shown below.
• For details on setting the terminal resistance of NT-AL001, refer to Set-
tings at the RS-232C/RS-422A Adapter (NT-AL001) (page 81).
5-2 Connecting to the Host’s RS-422A/485 Port
The methods for connecting the RS-422A/485 port of the NT631/NT631C and
the RS-422A/485 port of the host are described here. There are the following
methods.
The following discussion is focused on the connection method to OMRON
PLCs (By using the memory link method, a connection can be made to any
arbitrary RS-422 unit). When making a connection to a host other than
OMRON PLCs, refer to the PLC Connection Manual (V042-E1-@) or Multi
Vendor Connection Manual (V060-E1-@).
• Method in which the RS-422A ports of the NT631/NT631C and host are
connected directly by an RS-422A cable (page 115).
When this method is used, the cable length can be extended up to
500 m.
• Method in which the RS-485 ports of the NT631/NT631C and host are
connected by an RS-485 cable (page 118).
When this method is used, the cable length can be extended up to
500 m.
This connection method can be used only with the NT Link (1:N) meth-
od (standard or high-speed) of type RS-485.
• Method in which the RS-422A ports of multiple NT631/NT631Cs and the
RS-422A port of the host are connected in a 1:N connection (page 119).
This connection method is used with the RS-422A NT Link (1:N) meth-
od (standard or high-speed).
• Method in which the RS-485 ports of multiple NT631/NT631Cs and the
RS-485 port of the host are connected in a 1:N connection (page 121).
Terminal resistor (120 Ω)
RDB
RDA
TRM
+
-
Making a connection here inserts a terminator between
+ (RDB) and - (RDA).
PT Host
RS-422A cable
(max. 500 m)
PT Host
RS-485 cable
(max. 500 m)
PT
Host
RS-422A cable
(max. total length 500 m)