FlexRay Communication Controller (FlexRAY)
PXN20 Microcontroller Reference Manual, Rev. 1
26-118 Freescale Semiconductor
26.6.6.4.3 Message Buffer Transitions
Application Transitions
The application transitions that can be triggered by the application using the commands described in
Table 26-109. 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 can be issued on the transmit side only. Any enable or disable command
issued on the commit side will be ignored without notification. The transitions that will be triggered
depends on the value of the EDS bit. The enable and disable commands will affect both the commit side
and the transmit side at the same time. If the application triggers the disable transition HD while the
transmit side is in one of the states CCSa, CCSaCCITx, CCNf, CCNfCCITx, CCMa, CCMaCCITx, CCTx,
or CCSu, 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 can be issued on the commit side only. Any lock or unlock command
issued on the transmit side will be ignored and the double transmit buffer lock error flag DBL_EF in the
CHI Error Flag Register (CHIERFR) will be set. The transitions that will be triggered depends on the
current value of the LCKS bit. The lock and unlock commands will only affect the commit side. If the
application triggers the lock transition HL while the commit side is in the state CCITx, the message buffer
state will not be changed and the message buffer lock error flag LCK_EF in the CHI Error Flag Register
(CHIERFR) will be set.
CCTx 1 0 – TX Message Transmission - Message buffer data transmit. Payload data
from buffer transmitted
CCSu 1 0 – SS S
tatus Update - Message buffer status update. Update of status
flags, the slot status field, and the header index.
Note: The slot status field of the commit side is updated too, even if
the application has locked the commit side.
Table 26-109. Double Transmit Message Buffer Host Transitions
Transition Host Command Condition Description
HE
MBCCSR(2n +1)[EDT]=1
MBCCSR(2n + 1)[EDS] = 0 Application triggers message buffer enable.
HD MBCCSR(2n+1)[EDS] = 1 Application triggers message buffer disable.
HL
MBCCSR(2n)[LCKT] = 1
MBCCSR(2n)[LCKS] = 0 Application triggers message buffer lock.
HU MBCCSR(2n)[LCKS] = 1 Application triggers message buffer unlock.
Table 26-108. Double Transmit Message Buffer State Description (Transmit Side) (continued)
State
MBCCSRn Access Region
Description
EDS LCKS Appl. Module
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