What is the Mtype 29/Code 56 in AC450 ?
Mtype 29 is reserved for errors originating from VxWorks OS which was used to develop a number of communication modules for AC450, e.g MODBUS (CI534) but I suspect also the GCOM (CI543) was made with VxWorks.
The link below is possible to use on ABB Intranet, I suspect you can search for the documents, e.g. 3BSE010719R101 using SolutionsBank as well if you have an account there.
If you had submitted the complete system message with task name, trace address, Data1 and Data2 we might have been able to say something more...
<mtype> <code> <taskname> <address> <data1> <data2>
In any case; I suggest contacting your regional ABB support center for assitance as most of the error codes suggest contacting ABB.