Omron Programmable Terminals NT31 NT31C - Manual (Page 111)

5-2 Section Connecting to the Host’s RS-422A/485 Port
100
In order to set the terminal resistance, wiring work is required at the cable’s con-
nector: carry out the wiring correctly by referring to APPENDIX E Making the
Cable, page 267.
Abbreviation
FG
-
-
TRM
RDB (+)
SDB (+)
-
-
-
Pin number
Connector
hood
-
9
10
11
12
-
25
Terminal resistor setting
Pin Nos. 9 and 10 Function
Shorted
Terminal resistance is applied.
Short only at the NT31/NT31C connected to the end of an
RS-422A/485 cable.
Open
Terminal resistance is not applied.
Leave the terminals open when connecting an NT31/NT31C
anywhere other than at the end of the RS-422A/485 cable.
Note Before connecting or disconnecting cables between devices, make sure that the
power supply to all of the connected devices (NT31/NT31C, PC, etc.) is OFF.
Reference:
S The internal circuit of the NT31/NT31C is shown below.
16 (RDA)
9 (TRM)
10 (RDB) +
−
Terminal resistor (120 Ω)
Making a connection here inserts a terminator between
+ (RDB) and
− (RDA).
S For details on setting the terminal resistance of NT-AL001-E, refer to Settings
at the RS-232C/RS-422A Convertor Unit (NT-AL001-E) (page 88).
5-2 Connecting to the Host’s RS-422A/485 Port
The methods for connecting the RS-422A/485 port of the NT31/NT31C and the
RS-422A/485 port of the host are described here. There are the following meth-
ods.
The following discussion is focused on the connection method to OMRON PCs
(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 PCs, re-
fer to the PC Connection Manual (V042-E1-
j) or Multi Vendor Connection
Manual (V060-E1- j).
• Method in which the RS-422A ports of the NT31/NT31C and host are con-
nected directly by an RS-422A cable (page 117).
When this method is used, the cable length can be extended up to 500 m.
PT Host
RS-422A cable
(max. 500 m)
• Method in which the RS-485 ports of the NT31/NT31C and host are connected
by an RS-485 cable (page 121).
When this method is used, the cable length can be extended up to 500 m.