57.7.9.7 LON Node Backlog Estimation

As defined in CEA-709, the LON node maintains its own backlog estimation. The node backlog estimation is initially set to one, will always be greater than 1 and will never exceed 63. If the node backlog estimation exceeds the maximum backlog value, the backlog value is set to 63 and a backlog overflow error flag is set (LBLOVFE flag).

The node backlog estimation is incremented each time a frame is sent or received successfully. The increment to the backlog is encoded into the link layer header, and represents the number of messages that the packet shall cause to be generated upon reception.

The backlog decrements under one of the following conditions:

On waiting to transmit: If Wbase randomizing slots go by without channel activity.
On receive: If a packet is received with a backlog increment of ‘0’.
On transmit: If a packet is transmitted with a backlog increment of ‘0’.
On idle: If a packet cycle time expires without channel activity.