FlexRay Communication Controller (FlexRAY)
PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor 26-111
same time as the application locks the message buffer by the HL transition, the intermediate state is CCRx
and the resulting state is locked buffer subscribed state HLckCCRx.
26.6.6.3.2 Message Reception
As a result of the message buffer search, the controller changes the state of as many as two enabled receive
message buffers from either idle state Idle or locked state HLck to the either subscribed state CCBs or
locked buffer subscribed state HLckCCBs by triggering the buffer subscribed transition BS.
If the receive message buffers for the next slot are assigned to both channels, then at most one receive
message buffer is changed to a buffer subscribed state.
If more than one matching message buffers assigned to a certain channel, then only the message buffer
with the lowest message buffer number is in one of the states mentioned above.
With the start of the next static or dynamic slot the module trigger the slot start transition SLS. This
changes the state of the subscribed receive message buffers from either CCBs to CCRx or from
HLckCCBs to HLckCCRx, respectively.
During the reception slot, the received frame data are written into the shadow buffers. For details on
receive shadow buffers, see Section 26.6.6.3.5, Receive Shadow Buffers Concept. The data and status of
the receive message buffers that are the CCRx or HLckCCRx are not modified in the reception slot.
26.6.6.3.3 Message Buffer Update
With the start of the next static or dynamic slot or with the start of the symbol window or NIT, the module
triggers the slot or segment start transition SSS. This transition changes the state of the receiving receive
message buffers from either CCRx to CCSu or from HLckCCRx to HLck, respectively.
If a message buffer was in the locked state HLckCCRx, no update will be performed. The received data
are lost. This is indicated by setting the Frame Lost Channel A/B Error Flag FRLA_EF/FRLB_EF in the
CHI Error Flag Register (CHIERFR).
If a message buffer was in the CCRx state it is now in the CCSu state. After the evaluation of the slot status
provided by the PE the message buffer is updated. The message buffer update depends on the slot status
bits and the segment the message buffer is assigned to. This is described in Table 26-105.
Table 26-104. Receive Message Buffer Transition Priorities
State Priorities Description
module vs. application
Idle BS > HD Buffer Subscribed > Message Buffer Disable
HLck BS > HD Buffer Subscribed > Message Buffer Disable
CCRx SSS > HL Slot or Segment Start > Message Buffer Lock
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