# acu_behaviour field

The acu_behaviour field in ISDN_PROTOCOL_PARMS_Q931CC determines what automatic responses the ACU layer makes. Refer to isdnparm.h for more details.

The bit settings in this field are ignored when the protocol stack is started in channelized stack mode. Each bit set by the value in this field determines a particular element of the ACU layer's behavior. The values are defined as follows:

Value | Description
--- | ---
ACU_SEND_Q931_BUFFER | If this bit is set, the stack sends a whole received Q.931 message to the application, along with the ACU primitive.
ACU_SEND_D_CHANNEL_STATUS_CHANGE | If this bit is set, when the status of the D channel changes, an ACU_D_CHANNEL_STATUS_IN primitive is automatically sent to the application, indicating the change. The Acu_d_channel_state in this primitive indicates the status of the channel: 0 = OFF 1 = ON
ACU_SEND_UNKNOWN_FACILITY | If this bit is set, the stack sends the application an ACU_FACILITY_IN message containing the whole Q.931 buffer with the unknown facility IE. Setting this flag automatically enables the NS_ACCEPT_UNKNOWN_FAC_IE behavior bit.
ACU_BEHAVIOUR_NIL | This is the default value corresponding to the behavior of the ACU entity if neither of the previous bits are set.

If acu_behaviour is set to 0 or not set at all, the ISDN protocol stack behaves as if the ACU_BEHAVIOUR_NIL bit is set.