User`s manual

Western Reserve Controls, Inc. 1782-JDC User’s Manual
17
o 121 ohm
o 1% metal film
o 1/4 Watt
An appropriate terminating resistor, WRC part number RM121DN, may be purchased from
WRC.
IMPORTANT: Per the DeviceNet spec -- do not terminate devices on drop lines.
4.4.2 DeviceNet Connection Wiring
The JDC uses a 5-pin plug-style DeviceNet connector, which has male pins.
Figure 4-2 DeviceNet cable connector
4.4.3 RS485 Network Termination (1782-JDC-2, 1782-JDC-4)
It is common practice to terminate an RS485 network system at each end of the serial cable
to eliminate electrical reflections. An appropriate value for the terminating resistor typically is:
• 100-120 ohm, depending upon the characteristic impedance of the cable used
o 121 ohms (same value as the DeviceNet terminator) is a standard resistor value
that may be used in many cases
• 1% metal film
• 1/4 Watt
Correct cable termination is the responsibility of the user. The 1782-JDC-2 does not include
an internal terminating resistor.
Note: 1782-JDC-2 products shipped with date code “0338” and earlier may have an internal
220-ohm terminating resistor installed. If you have any questions about this, please contact
WRC by phone or at [e-mail].