FlexRay Communication Controller (FLEXRAY)
MPC5510 Microcontroller Family Reference Manual, Rev. 1
30-102
Freescale Semiconductor
Preliminary
Figure 30-114. Message Transmission Timing
Figure 30-115. Message Transmission from HLck state with unlock
The amount of message data read from the FRM and transferred to the FlexRay bus is determined by the
following three items
1. the message buffer segment that the message buffer is assigned to, as defined by the
Buffer Segment Size and Utilization Register (MBSSUTR)
.
2. the message buffer data field size, as defined by the related field of the
3. the value of the PLDLEN field in the message buffer header field, as described in
Section 30.6.5.2.1, “Frame Header Section Description
If a message buffer is assigned to message buffer segment 1, and PLDLEN > MBSEG1DS, then
2 * MBSEG1DS bytes will be read from the message buffer data field and zero padding is used for the
remaining bytes for the FlexRay bus transfer. If PLDLEN <= MBSEG1DS, the FlexRay block reads and
transfers 2*PLDLEN bytes. The same holds for segment 2 and MBSEG2DS.
30.6.6.2.6
Null Frame Transmission
A static slot with slot number S is assigned to the FlexRay block for channel A, if at least one transmit
message buffer is configured with the MBFIDRn.FID set to S and MBCCFRn.CHA set to 1. A Null Frame
is transmitted in the static slot S on channel A, if this slot is assigned to the FlexRay block for channel A,
and all transmit message buffers with MBFIDRn.FID = s and MBCCFRn.CHA = 1 are either not
committed, i.e MBCCSRn.CMT = 0, or locked by the application, i.e. MBCCSRn.LCKS = 1, or the cycle
counter filter is enabled and does not match.
Additionally, the application can clear the commit bit of a message buffer that is in the CCMa state, which
is called
uncommit
or
transmit abort
. This message buffer will be used for null frame transmission.
As a result of the message buffer search described in
Section 30.6.7, “Individual Message Buffer Search
the FlexRay block triggers the slot assigned transition SA for up to two transmit message buffers if at least
search[s+1]
MT
st
art
MA
slot s
TX
SU
CCMa
CCTx
slot s+1
Idle
MT
sta
rt
Idle
slot s+2
slot star
t
slot star
t
slot star
t
MT
st
art
message transmit
SSS
CCSu
search[s+1]
MT
st
art
MT
sta
rt
MA
slot s
TX
SSS
HLckCCMa CCTx
slot s+1
HLck
MT
st
art
Idle
slot s+2
slot st
art
slot s
tart
slot s
tart
HU
CCMa
message transmit