8.1 Introduction

8 ACU Message Primitives

8.1 Introduction

This chapter describes the types and contents of the messages interchanged between the ACU and the application program.

To send a message to the ACU, the application specifies the message primitive in the ISDN_MESSAGE structure passed to isdnSendMessage, as described in Section 0. Events received from the ACU contain message primitives, as described in Section 3.6.

8.1.1 About Macros

In the messages, most fields are accessible through macros, rather than directly. This is because the fields do not correspond to actual C language structure fields, and need some simple addressing computation to be reached. These macros are defined in isdnacu.h.

The following code fragment shows how to use macros to assign values to fields in an ACU message structure:

void build_cc_conn_rs(char *buffer, int *len, char ts)    
{    
    struct acu_conn_rs_args *p_data;
    
    p_data = (struct acu_conn_rs_args *)buffer;
    
    memset(p_data, OFF, ISDN_BUFFER_DATA_LGTH);
    
    /* Fill in three fields using macros*/
    
    Acu_conn_rs_service = ACU_VOICE_SERVICE;  /* type of service */    
    Acu_conn_rs_data_chani = ts;              /* T1/E1 time-slot */    
    Acu_conn_rs_data_chani_nb = 1;            /* only one B channel */
    
    /* User to user information could go here */
    
    *len = sizeof( struct acu_conn_rs_args );    
    return;    
}

8.1.2 ACU Message Structure Summary

The following is a summary of supported ACU messages:

Message Type	Description
ACU_ALERT_IN	Alert indication.
ACU_ALERT_RQ	Send an Alert message.
ACU_CLEAR_CO	Release confirmation.
ACU_CLEAR_IN	Release indication.
ACU_CLEAR_RQ	Release request.
ACU_CLEAR_RS	Response to the release.
ACU_CONN_CO	Call connection confirmation.
ACU_CONN_IN	Signals an incoming call.
ACU_CONN_RQ	Request establishment of an outgoing call.
ACU_CONN_RS	Answering an incoming call.
ACU_DIGIT_IN	Receive called number digits in overlap receiving mode.
ACU_PROGRESS_IN	Outgoing call progression information (receipt of Call-Proceeding or Progress message).
ACU_SETUP_REPORT_IN	Signals an incoming call that has been rejected or ignored by the ACU because it was not compatible (address or service filtering). The application must not answer to this incoming call indication. This message is only for information purposes.

Note: Not all macros or macro combinations are supported for every variant.

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