Bitronics M651, Руководство пользователя, Страница: 32 / 80

32
ML0039 November 14, 2013 Copyright 2013 Bitronics, LLC
4.0 OPERATION
4.1 Serial Port
This port when ordered can be set to RS-232 or RS-485, and support baud rates up to
115200. Set-up of the Serial Port can be accomplished by using a web browser
connected to the Ethernet port, or via the front display buttons (Setup menu -
1.4
Serial). The default configuration for the serial ports is:
Serial Port Default Setting
Port
Protocol Parity Baud
IED
Physical Media
Serial DNP 3 None 9600 1 RS-232
Serial cable requirements for RS485 connection:
Tie RS-485 cable shields (pin 15) to earth ground at one point in system.
The recommended torque ratings for the terminal block wire fasteners are listed in the
Physical Specifications table (section 1.3).
Transient Voltage Suppressor (TVS) clamp devices are used on the serial port as the
method of protection. The serial port is clamped to a voltage of 16.7-18.5V nominal,
24.46V max. The clamps are rated for a peak pulse current of 24.6 max.
4.1.1 RS485 Connections
Note that various protocols and services have different port connection requirements.
When making connections to serial ports for Modbus or DNP3 over RS485, 2-wire half
duplex is required. This is because it is imperative to maintain a minimum time period
(3 1/3 characters) from the time the transmitter shuts off to the next message on the
bus in order to guarantee reliable communications. See figure 5 below for RS485
cable wiring diagrams.