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Chapter 13 FlexRay Communication Controller (FLEXRAY)
MC9S12XF - Family Reference Manual, Rev.1.19
570
Freescale Semiconductor
Module Transitions
The module transitions that can be triggered by the FlexRay block are described in
Table 13-101. Each
transition will be triggered for certain message buffers when the related condition is fullled.
Transition Priorities
The application can trigger only one transition at a time. There is no need to specify priorities among them.
As shown in
Table 13-102, the module transitions have a higher priority than the application transitions.
For all states except the CCRx state, a module transition and the application lock/unlock transition HL/HU
and can be executed at the same time. The result state is reached by rst applying the module transition
and subsequently the application transition to the intermediately reached state. For example, if the message
buffer is in the buffer subscribed state CCBs and the module triggers the slot start transition SLS at the
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.
13.6.6.3.2
Message Reception
As a result of the message buffer search, the FlexRay block changes the state of up to 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.
Table 13-101. Receive Message Buffer Module Transitions
Transition
Condition
Description
BS
slot match and
CycleCounter match
Buffer Subscribed - The message buffer lter matches next slot and cycle.
SLS
slot start
Slot Start - Start of either Static Slot or Dynamic Slot.
SNS
symbol window start or
NIT start
Symbol Window or NIT Start - Start of either Symbol Window or NIT.
SSS
slot start or
symbol window start or
NIT start
Slot or Segment Start - Start of either Static Slot, Dynamic Slot, Symbol
Window, or NIT.
SU
status updated
Status Updated - Slot Status eld, message buffer status ags, header index
updated. Interrupt ag set.
Table 13-102. 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