Eurotherm 6100, Руководство пользователя

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100/180MM DISTRIBUTED GRAPHIC RECORDER: USER GUIDE
Page 139 HA029324
Issue 11 Oct 14
4.3.15 Connections
INTRODUCTION
This allows the serial communications ports (RJ45 connectors) of the recorder to be confi gured. Two
modes of operation are available: ASCII (INPUT) and Modbus.
ASCII (INPUT)
This mode allows the recorder to receive simple ASCII messages from, for example, barcode readers,
Programmable Logic Controllers (PLCs), Global Positioning Systems (GPSs) (NMEA-0183 protocol) etc.
Messages are sent to as many groups as are set up to receive them, and become a part of these groups’
histories, and appear on vertical and horizontal trend displays in the following format:
Date and time Message Source
23/08/05 10:25:06 (Serial), Message of up to 85 characters
MODBUS RTU
This allows the recorder’s serial communications ‘port’ to be used as Modbus master or Modbus slave.
When acting as a master, the unit can communicate with up to either 16 slaves (standard) or 32 slaves (op-
tion). Use of the Serial port is complementary to the use of Ethernet connections.
Note: When confi guring a unit as a Modbus slave, it is recommended that the Instrument and
Point Confi gurations give easily identifi able instrument and point names (descriptors).
TERMINATION AND BIASSING
If the communications line is left open-ended, the end of the cable acts as a refl ector, returning what
can appear to be ‘true’ data signals back down the line. A receiver cannot distinguish between ‘true’
and refl ected data, with the result that the ‘true’ data is corrupted. In order to avoid this, a termination
resistor is fi tted across the line at the fi nal instrument. For this instrument, a terminating resistor can be
switched into or out of circuit, as shown in
section 2.2.2 .
Section 2.2.2 also gives a pinout for the RJ45 connectors.