Clarification on Enhanced RX FIFO Support in S32K312 FlexCAN

[Yogs]

Hi, Here it says it supportsAnd here it says only for CAN FDI am currently working with the S32K312 and would like some clarification regarding FlexCAN Enhanced RX FIFO support.

From my understanding, the S32K312 FlexCAN module supports the Legacy RX FIFO. However, while reviewing the reference manual, I found some sections indicating that Classical CAN supports the Enhanced RX FIFO, whereas other sections seem to suggest that Enhanced RX FIFO is not supported.

Could you please clarify whether the FlexCAN module in the S32K312 supports the Enhanced RX FIFO feature? If it is supported, are there any specific limitations or conditions that apply when using Classical CAN frames?

Any clarification or references to the relevant documentation would be greatly appreciated.

Thank you.

[Yogs]

Hi Peter,
Thank you for the response , had a few more queries regarding the same.

• If the MCR[FDEN] bit is disabled (FlexCAN operating in Classical CAN mode), can the controller still support the Enhanced RX FIFO for receiving Classical CAN messages?
• If Enhanced RX FIFO is supported in this configuration, is there any reference application, example project, or documentation that demonstrates its usage?
• Is it possible to configure the Enhanced RX FIFO directly through the MEX configuration tool, or does it require manual configuration in the application code?
  
  Thank you

[PetrS]

Hi,

Q: If the MCR[FDEN] bit is disabled (FlexCAN operating in Classical CAN mode), can the controller still support the Enhanced RX FIFO for receiving Classical CAN messages?
A: yes, even if FDEN=0 the enhanced RXFIFO can be enabled and FlexCAN accepts just classical CAN messages, either to regular MBs or this enhance RXFIFO, depending on filtering criteria set.

Q: If Enhanced RX FIFO is supported in this configuration, is there any reference application, example project, or documentation that demonstrates its usage?
A: you can refer to below example, it sets FlexCAN with FDEN=1, but you can easily disable it in config tool, if needed, together with payload and bit timing modification.
https://community.nxp.com/t5/S32K-Knowledge-Base/Example-S32K344-FlexCAN-Ip-TX-RX-EnhanceRXFIFO-test...

Q: Is it possible to configure the Enhanced RX FIFO directly through the MEX configuration tool, or does it require manual configuration in the application code?
A: There is only few configuration option within Config tool
- enable/disable enhanced RXFIFO
- number of standard and extended filter elements
- watermark setting
The filter table must be configured within code. Refer to above demo.

BR, Petr

[PetrS]

Hi,

Table 493 just say that legacy RXFIFO cannot be enabled and used if CAN FD feature (MCR[FDEN]) is enabled in FlexCAN module. Legacy RXFIFO is available on each FlexCAN instance, but it is not able to accept CAN FD messages, just classic CAN messages. That's why enhance RXFIFO was introduced, which can handle both.  

PetrS_1-1781524408183.png

Generally each FlexCAN instance supports CAN FD. Instances differs in number of available MBs and enhanced RXFIFO support.

PetrS_0-1781523991167.png

Enhance RXFIFO is necessary if user want to enable both the RXFIFO and CAN FD options. Enhance RXFIFO is able to store up to 20 messages (both classic CAN and CAN FD). But it is available only on single module (FlexCAN 0) on most S32K3 devices. 

For more info read chapters 73.3.8 Enhanced RX FIFO and 73.3.9 Legacy RX FIFO of the device RM.

BR, Petr