FlexRay Communication Controller (FlexRAY)
PXN20 Microcontroller Reference Manual, Rev. 1
26-102 Freescale Semiconductor
26.6.6.2.3 Message Buffer Transitions
Application Transitions
The application transitions can be triggered by the application using the commands described in
Table 26-97. The application issues the commands by writing to the Message Buffer Configuration,
Control, Status Registers (MBCCSRn). Only one command can be issued with one write access. Each
command is executed immediately. If the command is ignored, it must be issued again.
Message Buffer Enable and Disable
The enable and disable commands issued by writing 1 to the trigger bit MBCCSRn[EDT]. The transition
that will be triggered by each of these command depends on the current value of the status bit
MBCCSRn[EDS]. If the command triggers the disable transition HD and the message buffer is in one of
the states CCSa, HLckCCSa, CCMa, HLckCCMa, CCNf, HLckCCNf, or CCTx, the disable transition has
no effect (command is ignored) and the message buffer state is not changed. No notification is given to the
application.
Message Buffer Lock and Unlock
The lock and unlock commands issued by writing 1 to the trigger bit MBCCSRn[LCKT]. The transition
that will be triggered by each of these commands depends on the current value of the status bit
MBCCSRn[LCKS]. If the command triggers the lock transition HL and the message buffer is in the state
CCTx, the lock transition has no effect (command is ignored) and message buffer state is not changed. In
this case, the message buffer lock error flag LCK_EF in the CHI Error Flag Register (CHIERFR) is set.
Module Transitions
The module transitions that can be triggered by the controller are described in Table 26-98. Each transition
will be triggered for certain message buffers when the related condition is fulfilled.
CCSu 1 0 – TX Status Update - Message buffer status update. Update of status
flags, the slot status field, and the header index.
Table 26-97. Single Transmit Message Buffer Application Transitions
Transition Command Condition Description
HE
MBCCSRn[EDT] = 1
MBCCSRn[EDS] = 0 Application triggers message buffer enable.
HD MBCCSRn[EDS] = 1 Application triggers message buffer disable.
HL
MBCCSRn[LCKT] = 1
MBCCSRn[LCKS] = 0 Application triggers message buffer lock.
HU MBCCSRn[LCKS] = 1 Application triggers message buffer unlock.
Table 26-98. Single Transmit Message Buffer Module Transitions
Transition Condition Description
SA slot match and
static slot
S
lot Assigned - Message buffer is assigned to next static slot.
Table 26-96. Single Transmit Message Buffer State Description (continued)
State
MBCCSRn Access Region
Description
EDS LCKS Appl. Module
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