The alternate data feature has an impact on the sampling service. By default, the message look-up table will have an entry for each message address. It is possible to enables message discrimination using the message extended address field using the mxfASCBRxSamplingExtEnableSet() function. When this feature is enabled for a specific address, the message look-up table will have an entry for each Alternate Data Index (bit 12-13 of first data word) of this address. The alternate parameter value of mxfASCBRxSamplingSingleRead() function is used to choose a specific alternate data index.