M580 and system words %SW138 to %SW141.
The M580 PAC does not support the system words, %SW138 and %SW140.
The M580 does support the system words, %SW139 and %SW141 but requires the M580 CPU to use firmware 2.10 IR15 or higher.
These System Words were added to offset the starting address of variables which are accessed by Modbus requests.
This functionality was not supported by the Unity Simulator until Unity Pro version 13.1.
You must set the values of the 2 system words %SW139 and %SW141 using the “Initial value” mechanism. Do not use programming code to set the values. Otherwise, when using the PLC init command or setting %S0 to 1 or downloading an application, the 2 system words are set to 0000 and the behavior of Modbus server is wrong.
Failure to follow these instructions can result in death, serious injury, or equipment damage.