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Module Operation
1257
SPNU563A–March 2018
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FlexRay Module
Table 26-14. Assignment of Output Buffer Command Mask Bits
Position Access Bit Function
17 r RDSH Read Data Section Host access
16 r RHSH Read Header Section Host access
1 r/w RDSS Read Data Section Shadow
0 r/w RHSS Read Header Section Shadow
Table 26-15. Assignment of Output Buffer Command Request Bits
Position Access Bit Function
22-16 r OBRH(6-0) OBF Request Host, number of message buffer available for host access
15 r OBSYS OBF Busy Shadow, signals ongoing transfer from message RAM to OBF Shadow
9 r/w REQ Request Transfer from message RAM to OBF Shadow
8 r/w VIEW View OBF Shadow, swap OBF Shadow and OBF Host
6-0 r/w OBRS(6-0) OBF Request Shadow, number of message buffer for next request
26.2.12.3 FlexRay Protocol Controller Access to Message RAM
The two transient buffer RAMs (TBF A,B) are used to buffer the data for transfer between the two FlexRay
channel protocol controllers and the message RAM.
Each transient buffer RAM is built up as a double buffer, able to store two complete FlexRay messages.
There is always one buffer assigned to the corresponding protocol controller while the other one is
accessible by the message handler.
If, for example, the message handler writes the next message to be sent to transient buffer Tx, the
FlexRay Channel protocol controller can access transient buffer Rx to store the message it is currently
receiving. During transmission of the message stored in transient buffer Tx, the message handler transfers
the last received message stored in transient buffer Rx to the message RAM (if it passes acceptance
filtering) and updates the corresponding message buffer.
Data transfers between the transient buffer RAMs and the shift registers of the FlexRay channel protocol
controllers are done in words of 32 bit. This enables the use of a 32 bit shift register independent of the
length of the FlexRay messages.
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