Echelon OpenLDV User Manual

Page 74

Sending and Receiving Messages with the OpenLDV API

and request messages. When the OpenLDV application generates a response

to an uplink request message, it must save the tag value from the request,

and return the same tag value in the downlink response message.

priority

The priority field is set to indicate a message delivered with priority media

access, either uplink or downlink. When the OpenLDV application generates

a response to an uplink request message, it saves the priority attribute from

the request, and returns the response with the same priority. If the network

interface is configured without priority buffers, and a priority request is

received, the OpenLDV application sets the priority bit in the response, but

sends the response in a non-priority buffer.

path

The path field is set to 1 if the message should use the alternate path, and 0

(zero) if it should use the primary path. This feature is enabled only if the

alternate path bit is set. Alternate path is a feature of certain special-

purpose mode L

ORKS

transceivers.

completion code

The completion code field is set for an uplink completion event. Completion

code events are returned to the OpenLDV application for every downlink

(niCOMM) network message sent:

•

The MSG_SUCCEEDS (1) value indicates that the message was

successfully delivered.

•

The MSG_FAILS (2) value indicates that the message failed to be

delivered.

•

Set the completion code field to MSG_NOT_COMPL (0) for

application layer buffers that are not completion events.

Messages sent to the network driver with the niNETMGMT network

interface command do not have associated completion events.

address mode

Set the address mode bit to 1 for an explicitly addressed downlink message,

and specify the network address field as a SendAddrDtl structure (see

SendAddrDtl on page 67).
Set the address mode field to 0 for an implicitly addressed downlink message,

in which case the network address field is ignored, although it must be

present. In this case, the tag field is used as the index into the address table

of the Smart Transceiver or Neuron Chip in the network interface for the

destination address. For more information about the address table, see the

ISO/IEC 14908-1 protocol specification.
Set the address mode to 0 for downlink responses to uplink request messages

and network variable polls.
The address mode bit is ignored for local network management

(niNETMGMT) messages.