FlexRay Module Registers
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SPNU563A–March 2018
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FlexRay Module
26.3.2.6.4 Message Handler Constraints Flags (MHDF)
Some constraints exist for the Message Handler regarding VBUSclk frequency, Message RAM
configuration, and FlexRay bus traffic. In order to simplify software development, constraints violations are
reported by setting flags in the MHDF.
A flag is cleared by writing a 1 to the corresponding bit position. Writing a 0 has no effect on the flag. A
hardware reset will also clear the register. The register is reset when the communication controller leaves
CONFIG state, enters STARTUP state, or by CHI command CLEAR_RAMS.
Figure 26-165 and Table 26-145 illustrate this register.
Figure 26-165. Message Handler Constraints Flags (MHDF) [offset_CC = 31Ch]
31 16
Reserved
R-0
15 9 8 7 6 5 4 3 2 1 0
Reserved WAHP TNSA TNSB TBFB TBFA FNFB FNFA SNUB SNUA
R-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 26-145. Message Handler Constraint Flags (MHDF) Field Descriptions
Bit Field Value Description
31-9 Reserved 0 Reads return 0. Writes have no effect.
8 WAHP Write attempt to header partition. This flag is set by the communication controller when the message
handler tries to write message data into the header partition of the Message RAM due to faulty
configuration of a message buffer. The write attempt is not executed, to protect the header partition
from unintended write accesses.
0 No write attempt to header partition.
1 Write attempt to header partition.
7 TNSA Transmission Not Started Channel A. This flag is set by the CC when the Message Handler was not
ready to start a scheduled transmission on channel A at the action point of the configured slot.
0 No transmission is not started on channel A.
1 Transmission is not started on channel A.
6 TNSB Transmission Not Started Channel B. This flag is set by the CC when the Message Handler was not
ready to start a scheduled transmission on channel B at the action point of the configured slot.
0 No transmission is not started on channel B.
1 Transmission is not started on channel B.
5 TBFB Transient buffer access failure B. This flag is set by the communication controller when a read or write
access to TBF B requested by PRT B could not complete within the available time.
0 No TBF B access failure.
1 TBF B access failure.
4 TBFA Transient buffer access failure A. This flag is set by the communication controller when a read or write
access to TBF A requested by PRT A could not complete within the available time.
0 No TBF A access failure.
1 TBF A access failure.
3 FNFB Find sequence not finished channel B. This flag is set by the communication controller when the
Message Handler, due to overload condition, was not able to finish a find sequence (scan of Message
RAM for matching message buffer) with respect to channel B.
0 No find sequence is not finished for channel B.
1 Find sequence is not finished for channel B.
2 FNFA Find sequence not finished channel A. This flag is set by the communication controller when the
Message Handler, due to overload condition, was not able to finish a find sequence (scan of Message
RAM for matching message buffer) with respect to channel A.
0 No find sequence is not finished for channel A.
1 Find sequence is not finished for channel A.
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