topic S32K144 FlexCAN SUPV in S32K

S32K144 FlexCAN SUPV

Junkie — Tue, 15 Nov 2022 10:20:13 GMT

Hi, I met a problem when i access S32K144 FlexCAN_IMASK1 in user mode with CAN_MCR_SUPV=0 will cause BusFault, But the description of SUPV in RM is "0b - FlexCAN is in User mode. Affected registers allow both Supervisor and Unrestricted accesses.", I wonder it is normal ?

Re: S32K144 FlexCAN SUPV

Robin_Shen — Fri, 18 Nov 2022 10:15:27 GMT

Hi Junkie,

The MCR[SUPV]=1 by default(FlexCAN is in Supervisor mode). Did you change the bit in Freeze mode?

I try to debug the can_pal_s32k144 example in S32 SDK for S32K1xx RTM 4.0.2.

First breakpoint: access the IMASK1 when MCR[SUPV]=1 did not cause BusFault.

Second breakpoint: access the IMASK1 when MCR[SUPV]=0 did not cause BusFault.

Best Regards,
Robin
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Re: S32K144 FlexCAN SUPV

Junkie — Tue, 22 Nov 2022 08:39:03 GMT

Do you enter user mode when SUPV = 0 ? I try your method, if in Supervisor mode (control[bit0] = 0), The phenomenon is as what you say , but when control[bit0] = 1 in user mode, BusFault will happen.

Re: S32K144 FlexCAN SUPV

Robin_Shen — Wed, 23 Nov 2022 15:11:18 GMT

Sorry for my previous reply. The core was in Supervisor (privileged) mode, I forgot change it in User(Unprivileged) mode.

Also cause BusFault when I access S32K144 FlexCAN_IMASK1 in User(Unprivileged) mode with CAN_MCR_SUPV=0. It seems that it does not match Table 55-19. Access permissions of S32K-RM Rev14

I need to consult it with our AE team and will update as soon as I have their feedback.

Re: S32K144 FlexCAN SUPV

Junkie — Thu, 24 Nov 2022 01:21:10 GMT

Ok, thank you，I will wait for that.

Re: S32K144 FlexCAN SUPV

Robin_Shen — Tue, 06 Dec 2022 01:06:13 GMT

Thanks for sharing your solution to me:
I have solved the problem, user mode access FlexCAN register is prevented by AIPS, as AIPS->OPACRL[0]_TP5 = 1, access FlexCAN register only in supervisor mode.