Honeywell System 57 MODBUS Interface Module

Key Features

The 57 System MODBUS interface facilitates digital communication between the 57 System control system and an external computer system.

MODBUS is a widely supported digital data communication protocol that provides a standard set of commands that can be used for system data communication.

Two different interface modules support the most widely used electrical interface standards, 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 perform calibration and other procedures.

The MODBUS interface is typically used to connect a System 57 control system to a plant control system for centralised monitoring of system status, often with a graphical display.

The main features of the MODBUS interface are as follows.

Easy installation on engineering cards.

Compatible with the 5701. 5704 and 5704F control cards.

Simple field connection via DC input card terminal block for

Wiring up to 2.5mm² (14 AWG).

Operates as MODBUS RTU.

Supports MODBUS protocol functions 02. 03. 04. 06. and 16.

Provides sensor gas readings and alarm status for fault and prohibition,

Provides sensor gas readings and alarm status for A1. A2. A3. FIRE, STEL, LTEL, and rate alarms.

Sensor gas readings and alarm status for A1. A2. A3. FIRE, STEL, LTEL, and rate alarms.

Supports commands to inhibit, reset, zero, calibrate (span) and set alarm levels.

(range) and set alarm levels for all channels in the rack.

Supports RS485. RS422. and RS232 electrical standards.

Data signals are isolated from the system 57 power supply.

Asynchronous serial link with configurable baud rate, parity and stop bits.

Primary and secondary channel operation.

Half-duplex operation.

Multi-point transmission capability

Easily configured using engineering interface software.

Commonly Used Terms

The reader should be familiar with the following terms used in this instruction manual:

MODBUS: Modbus is a digital data communication protocol that provides a widely used set of standard commands by which system data can be transmitted to external devices.

RS485: RS485 is an electrical standard for transmitting digital data using twisted-pair wires carrying differential signals.

RS485 allows up to 32 transceiver nodes to be connected on a twisted-pair highway for "multiplexed" bidirectional operation over distances of up to 1.2 kilometres (3900 feet).

RS422: RS422 is an electrical standard for transmitting digital data using twisted pair wires carrying differential signals.

RS422 allows for the connection of a single driver and up to 10 receiver nodes on a highway, operating over distances of up to 1.2 kilometres (3.900 feet).

RS232 RS232 is an electrical standard for transmitting digital signals using multi-core cables RS232 allows two communication devices to be interconnected

RS232 allows two communication devices to be interconnected for bidirectional operation over distances of up to 15 metres (49 feet).

Baud Rate: A baud rate is a unit of signal speed equal to the number of discrete signal events per second. (Not necessarily the same as the number of bits per second).

Bit Rate: The rate at which bits are transmitted, usually measured in bits per second (b/s).

Parity Check: A technique used in electronic code transmission to detect individual bit errors in transmitted data bytes (characters).

Stop Bit: A method of indicating the end of a transmitted data byte (character) in electronic code transmission.

Full duplex: A communications system capable of simultaneous independent data transmission in both directions.

A communications system that can transmit data in either direction, but not simultaneously.

Simplex: A communication system capable of transmitting data in only one direction.

MULTI-POINT TRANSMISSION: A communication line shared by multiple devices or "nodes".

Node: An intelligent device in a data communications system that is capable of communicating.

Host: The host system is the main device that runs the control system. The host is usually a PLC, DCS, or SCADA graphics software package.