Propose add the following text at the end of section 148.4.7.1 P53 L24:
When D-PLCA functionality is enabled the node switches to the WAIT_BEACON state and waits for the reception of a BEACON. If no BEACON is detected before wait_beacon_timer_done and the coordinator role is allowed,
the node promotes itself as the D-PLCA coordinator by switching to the COORDINATOR state.
The D-PLCA coordinator always maintains the plca_node_count such that transmit opportunity plca_node_count-1 is always unused. This allows new D-PLCA nodes to be added to the mixing segment by claiming this unused
transmit opportunity. Upon detecting a node perform a hard claim on this transmit opportunity, the D-PLCA coordinator will switch to the INCREASE_NODE_COUNT state and increase plca_node_count by one to create a new unused transmit opportunity.
The D-PLCA coordinator also shrinks plca_node_count to accommodate D-PLCA nodes being removed from the network. When the coordinator detects that no node has a hard claim on the last two transmit opportunities of
the cycle it will switch to the REDUCE_NODE_COUNT state. In this state the coordinator will reduce plca_node_count to the highest hard claimed transmit opportunity, plus one to maintain an unused transmit opportunity at the end of the PLCA cycle.
Detection of a BEACON or a hard claim on transmit opportunity zero by the D-PLCA coordinator indicates the existence of another coordinator on the mixing segment. In this case, the D-PLCA coordinator switches to
the LEARNING state where it demotes itself as a D-PLCA follower and begins identifying a transmit opportunity that it may claim.
Upon detection of a BEACON, new D-PLCA followers switch to the LEARNING state where they monitor the mixing segment for one PLCA cycle to identify transmit opportunities that have a hard claim. At the end of the
PLCA cycle, the D-PLCA follower will select a free transmit opportunity that does not have a hard claim. The follower will continue to monitor all transmit opportunities maintaining a table of transmit opportunities that are claimed by other followers. Once
the follower has selected a transmit opportunity, if it later detects another follower perform a hard claim on the same transmit opportunity, it will select a new transmit opportunity that does not have a hard claim.
If at any time BEACONs cease to be regularly detected and plca_status fails, followers will switch back to the WAIT_BEACON state through DISABLED.
--
Tim Baggett
Technical Staff Engineer - Applications
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Microchip Technology, Inc.
Automotive Information Systems
8601 Ranch Rd 2222, Park Centre, Bldg. 3, Austin, TX 78730
Office: 512-334-8450
Tim.Baggett@xxxxxxxxxxxxx
www.microchip.com
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