TC1784
FlexRay™ Protocol Controller (E-Ray)
User´s Manual
20-223
V1.1, 2011-05
E-Ray, V3.13
•
Dynamic segment: channel A
or
channel B
Message Buffer 0 is dedicated to hold the startup Frame, the SYNC Frame, or the
designated single slot Frame as configured by TXST, TXSY, and TSM in the SUC
Configuration Register 1. In this case it can be reconfigured in “DEFAULT_CONFIG” or
“CONFIG” state only. This ensures that any node transmits at most one startup / SYNC
Frame per communication cycle. Transmission of startup / SYNC Frames from other
Message Buffers is not possible.
All other Message Buffers configured for transmission in static or dynamic segment are
reconfigurable during runtime. Due to the organization of the Data Partition in the
Message RAM (reference by data pointer), reconfiguration of the configured payload
length and the data pointer in the Header Section of a Message Buffer may lead to
erroneous configurations. If a Message Buffer is reconfigured during runtime it may
happen that this Message Buffer is not send out in the respective communication cycle.
The Communication Controller does not have the capability to calculate the Header
CRC. The Host is supposed to provide the Header CRCs for all transmit buffers. If
Network Management is required the Host has to set the PPIT bit in the Header Section
of the respective Message Buffer to 1 and write the Network Management information to
the Data Section of the Message Buffer (see
).
The payload length field configures the data payload length in 2-byte words. If the
configured payload length of a static transmit buffer is shorter than the payload length
configured for the static segment by SFDL in the Message Handler Configuration
Register 1, the Communication Controller generates padding byte to ensure that Frames
have proper physical length. The padding pattern is logical zero.
Each transmit buffer provides a transmission mode flag TXM that allows the Host to
configure the transmission mode for the transmit buffer in the static segment. If this bit is
set, the transmitter operates in the single-shot mode. If this bit is cleared, the transmitter
operates in the continuous mode. In dynamic segment the transmitter always works in
single-shot mode.
If a Message Buffer is configured in the continuous mode, the Communication Controller
does not reset the transmission request flag TXR after successful transmission. In this
case a Frame is sent out each time the Frame ID and cycle counter filter match. The TXR
flag can be reset by the Host by writing the respective Message Buffer number to the
Input Buffer Command Request register while bit
in the Input Buffer Command
Mask register is reset to 0.
If two or more transmit buffers are configured with the same Frame ID
and
cycle counter
filter value, the transmit buffer with the lowest Message Buffer number will be transmitted
in the respective slot.
20.6.8.4 Frame Transmission
To prepare a transmit buffer for transmission the following steps are required:
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