This example demonstrates how you might configure a Simple Modbus Scanner, in order for it to scan four Input Registers on a Modbus PLC.
Example:
A Simple Modbus scanner is to scan Input Registers in the range 300003 to 300006. The addressing at the Modbus PLC starts at 1.
Within Geo SCADA Expert, the Modbus Scanner is configured as follows:
Data Address:2
(A starting address of 300003 indicates that the first data address is the third register in the Input Register range. As the Modbus addressing starts at 1 and Geo SCADA Expert addressing starts at 0, a Data Address of 2 maps to the third register in the range.)
Data Length:4
(As the range 300003 to 300006 is 4 registers long.)
Address Base:1
(As the Modbus addressing for this particular PLC starts at 1.)
Location:Input Registers
The Source attribute for the scanner confirms that the scanner is configured to scan Input Registers 300003 to 300006:
MODBUS/TCP-8 502:Device 5, Input Registers - 3:00003-3:00006
(3:00003-3:00006 indicates a Modbus address range of 300003 to 300006—a range that contains Input Registers in this particular PLC)