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ISOM DIGIWARE - 546780C - SOCOMEC
9. COMMUNICATION
9.1. General information
ISOM Digiware communicates via RS485 using the Modbus protocol. RS485 communication is available at a single
point on the ISOM Digiware D-55 or D-75 display.
It takes place via an RS485 serial link (2- or 3-wire) in accordance with the Modbus RTU protocol.
With the RS485 link, ISOM Digiware can be connected directly to a PC to retrieve the data.
The Modbus protocol requires a dialogue with a master/slave structure. The mode of communication is the RTU
(Remote Terminal Unit). In a standard setup, an RS485 link enables the interconnection of 32 RS485 devices (ISOM
Digiware D-55 or D-75 counting as one device), to a PC or a PLC etc. over a distance of 1,200 metres.
Example of the architecture of an ISOM Digiware D-55 or D-75 screen:
Supervision
MODBUS TCP
Web server
WEBVIEW (ISOM Digiware D-75)
ISOM Digiware D-55 / D-75
Digiware terminals
9.2. RS485 and ISOM Digiware bus rule
A certain number of rules must be respected when ISOM Digiware is connected using RS485. These rules are set
out in the paragraphs below.
9 .2 .1 . Connection with the D-55 or D-75 screen
The ISOM Digiware D-55 or D-75 screen is a master device of the RS485 bus and links to the DIRIS Digiware bus. It
is used like an Ethernet gateway.
They can be placed anywhere in the RS485 link.
The following rules must be observed:
•
A 120 Ω resistor must be added at the start of the RS485 link
•
A 120 Ω resistor must be added at the end of the RS485 link
• A terminal must be added at the end of the Digiware bus.
You can show 32 devices on an ISOM Digiware D-55/D-75 display.
