The System 57 MODBUS Interface provides a facility for digital
communication between the System 57 Control System and an external
computer system.
MODBUS is a well supported digital data
communication protocol which provides a set of standard commands
by which system data can be communicated. Two different interface
modules are available to support the most widely used electrical
interface standards, thereby ensuring compatibility with most external
systems. Using the MODBUS Interface it is possible to read
configuration, alarm status and other information from any channel in
the rack and to perform calibration and other procedures.
The MODBUS Interface is commonly used to connect the System 57
Control System to plant control systems to provide central monitoring
of system status often with graphical display.
The principal features of the MODBUS Interface are:
Easily fitted to the Engineering Card.
Compatible with 5701, 5704 and 5704F Control Cards.
Simple field connections, via the DC Input Card terminal block, for
wire up to 2.5mm² (14 AWG).
Operates as a MODBUS RTU.
Supports functions 02, 03, 04, 06 and 16 of the MODBUS protocol.
Provides sensor gas readings and alarm status for Fault, Inhibit,
A1, A2, A3, FIRE, STEL, LTEL and Rate alarms from all channels
in the rack.
Supports commands to Inhibit, Reset, Normalise (zero), Calibrate
(span) and set Alarm Levels for all channels in the rack.
Supports RS485, RS422 and RS232 electrical standards.
Data signals isolated from System 57 power supply.
Asynchronous serial link configurable for baud rate, parity and stop
bits.
Primary and secondary channel operation.
Half duplex operation.
Multi-drop capability.
Easily configured using Engineering Interface Software.