Emerson MODBUS 485 Manuel D’Utilisation

Modbus protocol provides control and data acquisition, through query and response, between master 

and slave devices. This protocol comprises the rules for communication, controlling the message 

format between devices, how master and slave devices initiate communications, as well as unit 

identification, message-handling and error-checking.
The Liebert IntelliSlot

®

 485/IP card acts as a slave device on a network. This network can be a 

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

The Liebert IntelliSlot 485/IP interface card supports Modbus Remote Terminal Unit (RTU) 

transmission modes. See Table 2 below.

Each Modbus packet consists of these fields:

• Device Address
• Function Code
• Data Field(s)
• Error Check Field

The address field immediately follows the beginning of the frame and consists of 8-bits (RTU). This bit 

indicates the user-assigned address of the slave device that is to receive the message from the 

attached master device.
Each slave must be assigned a unique address. Only the addressed slave will respond to a query that 

contains its address.

EIA-485/422

2 wire

RTU

9600, 19200

or 38400

8

None

1

1