Ge P485 Manuel d'utilisateur télécharger pdf (Page 45)

FRAME AND COMMAND EDITORS

P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE 6–3

SPECIFYING A NEW

COMMAND

Select ‘Add Command’ as described earlier.

This example is taken from a Modbus RTU implementation, which means that the frame

will always consist of one byte for slave address, one byte for function code and two bytes

for CRC. Furthermore, each command always consists of a query and a response.

The Modbus RTU specific frame objects are already in place and a data object is inserted

between the function code and the CRC. These objects cannot be moved or deleted,

however it is possible to add objects between the function code and the CRC.

Figure 6-4: Specifying a new command

First, enter a name for the command in the Command Name field (A) and an identifier in

the Command ID field (B). If the command is allowed to be broadcast on the sub-network,

check the Allow Broadcasting check box (C).

The Query (D) field has the following characteristics:

Query Column

1: Slave Address. 2: Modbus Function Code 3: See below 4: Error Check field.

DisplayName Slave Address Function Data Checksum

Protocol specific; cannot be altered. (See below)

Object Type Byte Byte Data Checksum

Modbus defines this object as a byte. (See below)

Value [SlaveAddress] ID User User

Linked to the actual ‘Slave

Address’ parameter in the

parameter window.

This value is linked to the

Command ID field.

(See below) Linked to “User”.

Determined by user at

configuration by selecting

the Error Check object in

the parameter window.

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Ge P485 Manuel d'utilisateur Page 45