ModMaster Manual v3.11 - 7. Tracing
ModMaster can trace all raw data that is sent or received, each Modbus message that is sent or received, and each register value read or written. The Tracing page is used to configure the categories of tracing.
The trace output is logged at Trace level (and so can normally be viewed using the → menu option). Trace output can be turned on and off using the Trace button on the toolbar.