Echelon Neuron C Manuel d'utilisateur télécharger pdf (Page 154)

142 How Devices Communicate Using Application Messages

sends any repeated requests to the application and the application must

regenerate the response. This provides the opportunity for the application to

update the response to a repeated request. If the application wants to treat these

repeated request messages as non-idempotent, it can do so by buffering responses

by receive transaction index and re-issuing those responses when duplicate

requests arrive. An example is shown below.

Example:

#define OK 1

#define MAXRESP 10

struct RespBuffer {

int code;

unsigned int len;

int data[MAXRESP];

} resp_buffer[16];

when (msg_arrives) {

struct RespBuffer *buf_p;

if (msg_in.service == REQUEST) {

buf_p = &resp_buffer[msg_in.rcvtx];

if (!msg_in.duplicate) {

int i;

// Process initial request

// . . .

// Now save response

buf_p->code = OK;

buf_p->len = MAXRESP;

for (i=0; i<MAXRESP; i++) {

buf_p->data[i] = get_resp_data();

}

// Generate the response.

resp_out.code = buf_p->code;

memcpy(resp_out.data, buf_p->data, buf_p->len);

resp_send();

}

The above example also shows that the rcvtx field of the msg_in object specifies

the receive transaction index to which the request belongs.

Application Buffers

You can set the number of incoming and outgoing buffers available for use by a

Neuron C application during compilation. The defaults for all models of the

Neuron Chip and the Smart Transceivers, except the Neuron 3120 Chip and the

Neuron 3120E1 Chip, are:

• Two priority application output buffers

• Two nonpriority application output buffers

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Echelon Neuron C Manuel d'utilisateur Page 154

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