NXP Semiconductors MPC5644A, Reference Manual, Page: 1584 / 1735

FlexRay Communication Controller (FlexRay)
MPC5644A Microcontroller Reference Manual, Rev. 6
1584 Freescale Semiconductor
33.6.9.8 FIFO update
The application updates the FIFOA (FIFOB) by writing a pop count value pc different from 0 to the
PCA (PCB) field in the Receive FIFO Fill Level and POP Count Register (FR_RFFLPCR) .
As a result of the this operation, the CC removes the oldest pc entries from FIFOA (FIFOB).
If the specified pop count value pc is greater than the current fill level fl provided in FLA (FAB) field, then
only fl entries are removed from the FIFOA (FIFOB), the remaining fl-pc requested pop operations are
discarded without any notification. In this case FIFOA (FIFOB) is empty after the update operation.
The read index in the Receive FIFO A Read Index Register (FR_RFARIR) ( Receive FIFO B Read Index
Register (FR_RFBRIR) ) is incremented by the number of removed items. If the read index reaches the top
of the FIFO, it wraps around to the FIFO start index defined in Receive FIFO Start Index Register
(FR_RFSIR) automatically.
33.6.9.8.1 FIFO interrupt flag update
Th FIFO Interrupt Flag Update mode is configured when the FIFO update mode flag FR_MCR[FUM] is
set to ‘0’. In this mode FIFOA (FIFOB) will be updated by one entry, when the interrupt flag
FR_GIFER[FAFAIF] (FR_GIFER[FAFBIF]) is written with ‘1’ by the application.
If the FIFO is empty, the update request is ignored without any notification.
The read index in the Receive FIFO A Read Index Register (FR_RFARIR) ( Receive FIFO B Read Index
Register (FR_RFBRIR) ) is incremented by 1 if the FIFO was not empty. If the read index reaches the top
of the FIFO, it wraps around to the FIFO start index automatically.
33.6.9.9 FIFO filtering
The FIFO filtering is activated after all enabled individual receive message buffers have been searched
without success for a message buffer to receive the current frame.
The CC provides three sets of FIFO filters. The FIFO filters are applied to valid non-null frames only. The
FIFO will not receive invalid or null-frames. For each FIFO filter, the pass criteria is specified in the
related section given below. Only frames that have passed all filters will be appended to the FIFO. The
FIFO filter path is depicted in
Figure 33-148 .