FlexRay Communication Controller (FLEXRAY)
MPC5510 Microcontroller Family Reference Manual, Rev. 1
Freescale Semiconductor
30-119
Preliminary
Figure 30-128. Internal Message Transfer in Immediate Commit Mode
30.6.6.4.6
Message Transmission
For double transmit message buffers, the message buffer search checks only the transmit side part. The
internal scheduling ensures, that the internal message transfer is stopped on the message buffer search start.
Thus, the transmit side of message buffer, that is not in its transmission or status update slot, is always in
the Idle state.
The message transmit behavior and transmission state changes of the transmit side of a double transmit
message buffer are the same as for single buffered transmit buffers, except that the transmit side of double
buffers can not be locked by the application, i.e. the HU and HL transition do not exist. Therefore, refer to
Section 30.6.6.2.5, “Message Transmission”
30.6.6.4.7
Message Buffer Status Update
The message buffer status update behavior of the transmit side of a double transmit message buffer is the
same as for single transmit message buffers which is described in
Section 30.6.6.2.7, “Message Buffer
Additionally, the slot status field of the commit side is update after the update of the slot status field of the
transmit side, even if the commit side is locked by the application. This is implemented to provide the slot
status of the most recent transmission slot.
30.6.7
Individual Message Buffer Search
This section provides a detailed description of the message buffer search algorithm.
The message buffer search determines for each enabled channel if a slot
s
in a communication cycle
c
is
assigned for frame or null frame transmission or if it is subscribed for frame reception on that channel.
The message buffer search is a sequential algorithm which is invoked at the following protocol related
events:
1. NIT start
2. slot start in the static segment
3. minislot start in the dynamic segment
Idle
Commit
T
ransmit
Idle
HL
HLck
Si
de
Side
slot s
slot s+1
slot s+2
search[s+1]
slot
st
art
slot start
slot start
HU
CCITx
Idle
IS
CCITx
IE
Idle
HL
HLck
HU
Idle
CCITx
Idle
IS
CCITx
IE
Idle
Idle
internal message transfer
overwrites non-transmitted message