Modbus

Modicon Format

When converting from Modicon to SCADACore format for the registers there are 4 options. Most of the time the format will be as follows with the SCADACore register format on the end.

0x = Coil = 00001-09999 = 1,x
1x = Discrete Input = 10001-19999 = 2,x
3x = Input Register = 30001-39999 = 3,x
4x = Holding Register = 40001-49999 = 4,x

For example a Register of 12 is a Coil register. For SCADACore the register format is 1,12.

Note: There are several PLCs that swap the 30000 and 40000. SCADAPacks for example use 40000 as 3,x and 30000 as 4,x

Schneider % Addressing

For Schneider Modbus devices they use the % style of addressing. This is common in the new Eco Struxure devices.

• %Q = Coil = 1,x
• %I = Discrete = 2,x
• %MW = Holding = 3,x
• %IW = Input = 4,x

The % addressing is often Zero Offset

One Offset vs Zero Offset

Depending on the PLC you may have a Zero Offset or a One Offset.

SCADACore registers work on a 1 offset if you have a Modicon format 40001-49999 it is very often a 1 offset (the first register is 1). In order to map them to a SCADACore register you need to subtract 1.

For example Register 40001 = 4,0.