Emerson Autochangeover Controllers AC8 Manual de usuario descargar pdf (Pagina 9)

Revision B.31 10/14/2009

Liebert Monitoring Group - Development

Page 9 of 146

Implementation Basics

Protocol controls the language structure or message format between devices in other words, the rules for

communication. The rules for communication include how master and slave devices initiate communications, as

well as unit identification, message handling and error checking. Modbus protocol simply refers to the control of

the query and response cycles between master and slave devices.

The SiteLink module is configured to act as a slave device on a common network. The common network can be

point-to-point over EIA-232, where one master communicates to one slave device or in a multi-drop configuration

over EIA-485, where multiple slaves reside on a common wire or loop.

Transmission Format

The SiteLink module supports both Modbus RTU (Remote Terminal Unit) and ASCII (American Standard Code for

Information Interchange) transmission modes. The SiteLink module has a choice of transmission medium, baud

rate, character parity and number of stop bits. See chart below.

Physical

Port

Transmission

Mode

Baud Rate Data Bits Parity Bits Stop Bits Default

EIA-232 –

DB9 DCE

RTU 9600 8 None 1 Yes

EIA-232 –

DB9 DCE

ASCII 1200 –

38.4kbd

(19.2kbd omit)

Configurable Configurable Configurable No

EIA-485 – 2

or 4 wire

RTU or ASCII 1200 –

38.4kbd

(19.2kbd omit)

Configurable Configurable Configurable No

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Emerson Autochangeover Controllers AC8 Manual de usuario Pagina 9