Echelon Neuron C - Manual (Page 152)

140 How Devices Communicate Using Application Messages
To use this field, you must include the <addrdefs.h> and
<msg_addr.h > files .
Request/Response Examples
This example shows sending a request and asynchronously receiving the
responses. The code for receiving this request and responding to it follows in the
next example.
msg_tag tag1;
#define DATA_REQUEST 0
when (io_changes(toggle))
{
msg_out.tag = TAG1;
msg_out.code = DATA_REQUEST;
msg_out.service = REQUEST;
msg_send();
}
when (resp_arrives(TAG1))
{
if (resp_in.code == OK)
process_response(resp_in.data[0]);
}
Here is the code for the responder to this request:
#define DATA_REQUEST 0
#define OK 1
when (msg_arrives(DATA_REQUEST))
{
int x, y;
x = msg_in.data[0];
y = get_response(x);
resp_out.code = OK;
// msg_in no longer available
resp_out.data[0] = y;
resp_send();
}
The following example shows sending a request and receiving the responses
directly:
int x;
msg_tag motor;
#define MOTOR_ON 0
#define DO_MOTOR_ON 3
when (command == DO_MOTOR_ON)
{
// send a request
msg_out.tag = motor; // construct the message
msg_out.code = MOTOR_ON;
msg_out.service = REQUEST;