Subclass for ARINC 664 channel works a little differently than for other channel classes. Subclass helps filtering the channels on direction (RX or TX) and services (Acquisition or Sampling), but since ARINC 664 physical channel is bidirectional, RX and TX channel is the same. Using MXF_SCLASS_ALL on an A664 module will have the same effect as using any of the following subclasses.

Reception

To get the physical 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.

Transmission

To get the physical 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.