Modbus Exception: Data Out of Range (Holding Register Write)

What does 21 hex mean?

This Modbus exception occurs specifically when writing to a holding register if the data value is outside the parameter's permissible range. It's a more specific version of 'Illegal Data Value' (03 hex) for write operations to holding registers. The inverter rejects the write to prevent parameters from being set to an invalid state.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   If Modbus mapping is used, check the 'Modbus Mapping Scaling' (P221 to P230) parameters to ensure that the data is not being scaled incorrectly before being written to the internal register.