Appendix A: Input Modules; Modbus Port - Siemens SITRANS RD500 Operating Instructions Manual

Appendix A: Input Modules

Modbus Port

Belden 9842 is a multi-conductor cable which is recommended for use with
Note:
RS-485 industrial networks. The cable comprises four conductors and an overall
braided shield. It is recommended that you use three of the four conductors for A,
B, and Common connections. The shield on the cable should be connected to
ground at one point to ensure best noise immunity.
The RD500 hardware includes an RS-485 Modbus RTU interface to field instruments
using an RJ-45 connector.
• Allows for long cable runs and multi-drop instrument connection.
• Address up to 247 Modbus instruments on a single two-wire network up to 1200 m
(3900 ft) away. Can be increased using a repeater and/or standard RS-485 network
equipment.
Notes:
• RS-485 wiring maximum length 1200 m (3900 ft)
Communication Settings
• Protocol Type = Modbus RTU and Modbus ASCII
• RTU Framing = Detect via Timing
• Slave Response Timeout = 1000
• Baudrate = selectable
• Databits = 1
• Parity = None
• Stopbits = 1
7ML19985MA01 SITRANS RD500 – OPERATING INSTRUCTIONS Page 37