This example demonstrates how you might configure a Simple Modbus Scanner, so that it scans a block of Output Coils in a Modbus PLC.
Example:
A Simple Modbus scanner is to scan Output Coils in the range 00006 to 00105. The addressing at the Modbus PLC starts at 1.
Within Geo SCADA Expert, the Simple Modbus Scanner is configured as follows:
Data Address:5
(A starting address of 00006 indicates that the first data address is the 6th coil in the Output Coils range. As the Modbus addressing starts at 1 and Geo SCADA Expert addressing starts at 0, a Data Address of 5 maps to the 6th Output Coil in the range.)
Data Length:100
(As the range 00006 to 00105 is 100 coils long.)
Address Base:1
(As the Modbus addressing for this particular PLC starts at 1.)
Location:Output Coils
The Source attribute for the scanner confirms that the scanner is configured to scan Output Coils 00006 to 00105:
MODBUS/TCP-8 502:Device 5, Output Coils - 0:00006-0:00105
(0:00006-0:00105 indicates a Modbus address range of 00006 to 00105—a range that contains Output Coils in this particular PLC)