GE P485 - Manual (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.