FlexRay Communication Controller (FLEXRAY)
Freescale Semiconductor
22-103
PXR40 Microcontroller Reference Manual, Rev. 1
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 controller reads and
transfers 2*PLDLEN bytes. The same holds for segment 2 and MBSEG2DS.
22.6.6.2.6
Null Frame Transmission
A static slot with slot number S is assigned to the controller 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 controller 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 22.6.7, Individual Message Buffer Search
the controller triggers the slot assigned transition SA for up to two transmit message buffers if at least one
of the conditions mentioned above is fulfilled for these message buffers. The transition SA changes the
message buffer states from either Idle to CCSa or from HLck to HLckCCSa. In each case, these message
buffers will be used for null frame transmission in the next slot. A message buffer timing and state change
diagram for null frame transmission from Idle state is given in
Figure 22-123. Null Frame Transmission from Idle state
A message buffer timing and state change diagram for null frame transmission from HLck state is given
in
Figure 22-124. Null Frame Transmission from HLck state
If a transmit message buffer is in the CCSa or HLckCCSa state at the start of the transmission slot, a null
frame is transmitted in any case, even if the message buffer is unlocked or committed before the
transmission slot starts. A transmit message buffer timing and state change diagram for null frame
transmission for this case is given in
search[s+1]
MT st
art
MT s
tar
t
SA
slot s
STS
SSS
CCSa CCNf
slot s+1
Idle
MT star
t
Idle
slot s+2
slot start
slot start
slot start
null frame transmit
search[s+1]
MT
star
t
MT
star
t
SA
slot s
STS
SSS
HLckCCSa HLckCCNf
slot s+1
HLck
MT s
tar
t
HLck
slot s+2
slo
t st
ar
t
slo
t st
ar
t
slo
t st
ar
t
null frame transmit
Summary of Contents for PXR4030
Page 1: ...PXR40 Microcontroller Reference Manual Devices Supported PXR4030 PXR4040 PXR40RM Rev 1 06 2011...
Page 30: ...PXR40 Microcontroller Reference Manual Rev 1 Freescale Semiconductor xxx...
Page 40: ...PXR40 Microcontroller Reference Manual Rev 1 xl Freescale Semiconductor...
Page 66: ...Memory Map PXR40 Microcontroller Reference Manual Rev 1 2 4 Freescale Semiconductor...
Page 120: ...Signal Descriptions 3 54 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Page 860: ...FlexCAN Module 24 50 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Page 1167: ...Decimation Filter Freescale Semiconductor 28 53 PXR40 Microcontroller Reference Manual Rev 1...
Page 1168: ...Decimation Filter 28 54 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...