FlexRay Communication Controller (FLEXRAY)
MPC5510 Microcontroller Family Reference Manual, Rev. 1
Freescale Semiconductor
30-117
Preliminary
30.6.6.4.4
Message Preparation
The application provides the message data through the commit side. The transmission itself is executed
from the transmit side. The transfer of the message data from the commit side to the transmit side is done
by the
Internal Message Transfer
Section 30.6.6.4.5, “Internal Message Transfer
To transmit a message over the FlexRay bus, the application writes the message data into the message
buffer data field of the commit side and sets the commit bit CMT in the
Control, Status Registers (MBCCSRn)
. The physical access to the message buffer data field is described
Section 30.6.3.1, “Individual Message Buffers
, the application shall write to the message buffer data field and change the
commit bit CMT only if the transmit message buffer is in one of the states HDis, HDisLck, or HLck. The
application can change the state of a message buffer if it issues the appropriate commands shown in
. The state change is indicated through the MBCCSRn.EDS and MBCCSRn.LCKS status
bits.
30.6.6.4.5
Internal Message Transfer
The internal message transfer transfers the message data from the commit side to the transmit side. The
internal message transfer is implemented as the swapping of the content of the
of the commit side and the transmit side. After the swapping, the commit side CMT
bit is cleared, the commit side interrupt flag MBIF is set, the transmit side CMT bit is set, and the transmit
side DVAL bit is cleared.
The conditions and the point in time when the internal message transfer is started are controlled by the
message buffer commit mode bit MCM in the
Message Buffer Configuration, Control, Status Registers
. The MCM bit configures the message buffer for either the streaming commit mode or the
immediate commit mode. A detailed description is given in
. The Internal Message Transfer is triggered with the transition IS. Both sides of the message
buffer enter one of the CCITx states. The internal message transfer is finished with the transition IE.
Streaming Commit Mode
The intention of the streaming commit mode is to ensure that each committed message is transmitted
at
least once
. The FlexRay block will not start the Internal Message Transfer for a message buffer as long as
the message data on the transmit side is not transmitted at least once.
Table 30-108. Double Transmit Message Buffer Transition Priorities
State
Priority Description
module vs. application
Idle
IS > HD
IS > HL
Internal Message Transfer Start > Message Buffer Disable
Internal Message Transfer Start > Message Buffer Lock
module internal
Idle
MA > SA
Message Available > Slot Assigned
CCMa
TX > STS
TX > DSS
Transmission Slot Start > Static Slot Start
Transmission Slot Start > Dynamic Slot Start