RM0440 Rev 4 1967/2126
RM0440 FD controller area network (FDCAN)
2008
Due to the fact that the CPU has free access to the FDCAN Message RAM, special care
has to be taken when reading FIFO elements in an arbitrary order (Get Index not
considered). This might be useful when reading a High Priority Message from one of the two
Rx FIFOs. In this case the FIFO Acknowledge Index must not be written because this would
set the Get Index to a wrong position and also alters the FIFO Fill Level. In this case some
of the older FIFO elements would be lost.
Note: The application has to ensure that a valid value is written to the FIFO Acknowledge Index.
The FDCAN does not check for erroneous values.
44.3.5 FDCAN Rx FIFO element
Two Rx FIFOs are configured in the Message RAM. Each Rx FIFO section can be
configured to store up to three received messages. The structure of an Rx FIFO element is
described in Table 396, the description is provided in Table 397.
The element size configured for storage of CAN FD messages is set to 64 bytes data field.
Table 396. Rx FIFO element
Bit 31 24 23 16 15 8 7 0
R0 ESI XTD RTR ID[28:0]
R1 ANMF FIDX[6:0] Res. FDF BRS DLC[3:0] RXTS[15:0]
R2 DB3[7:0] DB2[7:0] DB1[7:0] D[7:0]
R3 DB7[7:0] DB6[7:0] DB5[7:0] DB4[7:0]
...
...
...
...
Rn DBm[7:0] DBm-1[7:0] DBm-2[7:0] DBm-3[7:0]
Table 397. Rx FIFO element description
Field Description
R0 Bit 31
ESI
Error state indicator
– 0: Transmitting node is error active
– 1: Transmitting node is error passive
R0 Bit 30
XTD
Extended identifier
Signals to the Host whether the received frame has a standard or extended identifier.
– 0: 11-bit standard identifier
– 1: 29-bit extended identifier
R0 Bit 29
RTR
Remote transmission request
Signals to the Host whether the received frame is a data frame or a remote frame.
– 0: Received frame is a data frame
– 1: Received frame is a remote frame
R0 Bits 28:0
ID[28:0]
Identifier
Standard or extended identifier depending on bit XTD. A standard identifier is stored
into ID[28:18].
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