NXP Semiconductors MPC5644A, Reference Manual, Page: 1554 / 1735

FlexRay Communication Controller (FlexRay)
MPC5644A Microcontroller Reference Manual, Rev. 6
1554 Freescale Semiconductor
The trigger bits FR_MBCCSRn[EDT] and FR_MBCCSRn[LCKT], and the interrupt enable bit
FR_MBCCSRn[MBIE] are not under access control and can be accessed from the application at any time.
The status bits FR_MBCCSRn[EDS] and FR_MBCCSRn[LCKS] are not under access control and can be
accessed from the CC at any time.
The interrupt flag FR_MBCCSRn[MBIF] is not under access control and can be accessed from the
application and the CC at any time. CC clear access has higher priority.
The CC 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 33-130 . A description of the states is given in Table 33-106 , which also
provides the access scheme for the access regions.
The status bits FR_MBCCSRn[EDS] and FR_MBCCSRn[LCKS] provide the application with the
required message buffer status information. The internal status information is not visible to the application.
33.6.6.2.2 Message buffer states
This section describes the transmit message buffer states and provides a state diagram.
Table 33-105. 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