Specifying A New Command - GE D485 Instruction Manual

SPECIFYING A NEW
COMMAND
Query
1: Slave Address.
DisplayName Slave Address
Object Type
Value [SlaveAddress]
Linked to the actual 'Slave
Address' parameter in the
parameter window.
D485 MODBUS TO DEVICENET CONVERTER – USER GUIDE
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.
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:
2: Modbus Function Code
Function
Protocol specific; cannot be altered.
Byte
Modbus defines this object as a byte.
This value is linked to the
Command ID field.
Figure 6-4: Specifying a new command
Column
3: See below
Data
(See below)
Byte Data
(See below)
ID User
(See below)
FRAME AND COMMAND EDITORS
4: Error Check field.
Checksum
Checksum
User
Linked to "User".
Determined by user at
configuration by selecting
the Error Check object in
the parameter window.
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