The Web Browser
63 of 82
Publication S703E V1.1
Issue 06/09
Modbus Message Response
Address
: The address of the responding system, it will match the query address.
Function Code
: Modbus function code to read or write register, discrete or coil.
Data
: Modbus data reply, without a CRC. There will be no spaces in the data
field.
Example:
Read the number of field units connected to the system; generic database is set up. Refer to S171E
for the mapping of the Modbus registers. Number of FCUs is at master station register 0007.
Function code 03 (holding register read) can be used. The Modbus function would be:
Modbus Address
function code
register to start read
number of registers to read
01
03
00 07
00 01
The address and fundtion code should be entered in the relevant spaces and the data field should
contain the rest of the function, this field should be entered with no spaces. When the send query
button is pressed the result will be shown.
Here the data shows that 2 bytes of data are present in the message (02) and the data is 00 19. The
19hex is the number of field units fitted to the A side of the loop.
