For channel allocation of ARINC 429, subclasses are defined for the schemes of transmission and reception.

Subclasses help in filtering the channels on direction (RX or TX) and services (Acquisition, Sampling, Aperiodic transmit, etc.).

Reception

To get the receive channel handle, the following subclasses can be used:

Constant	Description
MXF_SCLASS_RX_CHANNEL	Generic receive channel
MXF_SCLASS_RXACQ_SRV	This subclass is used for the acquisition service.
MXF_SCLASS_RXSAMPLING_SRV	This subclass is used for the sampling service.

Transmission

To get the transmit channel handle, the following subclasses can be used:

Constant	Description
MXF_SCLASS_TX_CHANNEL	Generic transmission channel
MXF_SCLASS_TXAPERIODIC_SRV	This subclass is used for aperiodic messages transmission.
MXF_SCLASS_TXPERIODIC_SCHEDULE_SRV	This subclass is used for periodic messages transmission.
MXF_SCLASS_TXPERIODIC_UPDATEMSG_SRV	This subclass is used for periodic messages update transmission.