NXP Semiconductors PXN2020 - Page 714

FlexRay Communication Controller (FlexRAY)
PXN20 Microcontroller Reference Manual, Rev. 1
26-100 Freescale Semiconductor
Figure 26-119. Single Transmit Message Buffer Access Regions
The trigger bits MBCCSRn[EDT] and MBCCSRn[LCKT], and the interrupt enable bit
MBCCSRn[MBIE] are not under access control and can be accessed from the application at any time. The
status bits MBCCSRn[EDS] and MBCCSRn[LCKS] are not under access control and can be accessed
from the controller at any time.
The interrupt flag MBCCSRn[MBIF] is not under access control and can be accessed from the application
and the controller at any time. controller clear access has higher priority.
The controller restricts its access to the regions depending on the current state of the message buffer. The
application must adhere to these restrictions in order to ensure data consistency. The transmit message
buffer states are given in Figure 26-120. A description of the states is given in Table 26-96, which also
provides the access scheme for the access regions.
The status bits MBCCSRn[EDS] and MBCCSRn[LCKS] provide the application with the required
message buffer status information. The internal status information is not visible to the application.
26.6.6.2.2 Message Buffer States
This section describes the transmit message buffer states and provides a state diagram.
Table 26-95. Single Transmit Message Buffer Access Regions Description
Region
Access from
Region used for
Application Module
CFG read/write - Message Buffer Configuration
MSG read/write - Message Data and Slot Status Access
NF - read-only Message Header Access for Null Frame Transmission
TX - read/write Message Transmission and Slot Status Update
CM - read-only Message Buffer Validation
SR - read-only Message Buffer Search
Message Buffer Data Field: DATA[0-N]
Message Buffer Header Field: Frame Header
MBCCSRn[CMT]
Message Buffer Header Field: Slot Status
Message Buffer Header Field: Data Field Offset
MBCCFRn[MTM/CHA/CHB/CCF*]
MBFIDRn[FID]
MBIDXRn[MBIDX]
MBCCSRn[MBT/MTD]
TX
NF
CMT
SR
CFG
MSG