PXS20RM Datasheet, PDF (835/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

FlexRay Communication Controller
Message Buffer Status Update after Null Frame Transmission
After the transmission of a null frame, the status of the message buffer that was used for the null frame
transmission is not changed at all. The slot status field is not updated, the status and control flags are not
changed, and the interrupt flag is not set.
26.6.6.3 Receive Message Buffers
The section provides a detailed description of the functionality of the receive message buffers. If receive
message buffers are used it is required to configure the related receive shadow buffer as described in
Section 26.6.3.2, Receive Shadow Buffers.
A receive message buffer is used to receive a message from the FlexRay Bus based on individual filter
criteria. The CC uses the receive message buffer to provide the following data to the application
1. message data received
2. information about the reception process
3. status information about the slot in which the message was received
A individual message buffer with message buffer number n is configured as a receive message buffer by
the following configuration settings
• FR_MBCCSRn[MBT] = 0 (single buffered message buffer)
• FR_MBCCSRn[MTD] = 0 (receive message buffer)
To certain message buffer fields, both the application and the CC have access. To ensure data consistency,
a message buffer locking scheme is implemented that is used to control the access to the data, control, and
status bits of a message buffer. The access regions for receive message buffers are depicted in
Figure 26-137. A description of the regions is given in Table 26-110. If an region is active as indicated in
Table 26-111, the access scheme given for that region applies to the message buffer.
Message Buffer Header Field: Data Field Offset
CFG
Message Buffer Header Field: Frame Header
Message Buffer Header Field: Slot Status
RX
MSG
Message Buffer Data Field: DATA[0-N]
FR_MBIDXRn[MBIDX]
FR_MBCCSRn[DVAL/DUP]
FR_MBCCSRn[MTD]
FR_MBCCFRn[CHA/CHB/CCF*]
SR
FR_MBFIDRn[FID]
Figure 26-137. Receive Message Buffer Access Regions
Freescale Semiconductor
PXS20 Microcontroller Reference Manual, Rev. 1
26-123