S32K MPU Documentation

[ScottKerstein]

Hello,

I'm trying to understand the purpose of the MPU in the S32K micro.  Is there any reference manual or documentation that describes why and how I use the MPU?

Thanks in advance,

Scott

[lukaszadrapa]

Hi Scott,

MPU helps to prevent a process from accessing memory that has not been allocated to it. If you use operating system, each task can usually access only limited resources and MPU helps you to implement this protection.

MPU sits at the crossbar switch, so you can configure individual access rights to each master. There are eight region descriptors.

You can take a look at this SW example:

https://community.nxp.com/docs/DOC-332545 

It is written for MPC5748G but the principle is still the same. See the main.c.

Regards,

Lukas

[bernat_feixas1]

Hello,

Could you reload this example?

It appears as not accesible

Thanks

[ScottKerstein]

Thanks. 

 RESET pin filtering clarification.

Part is normally in RUN mode except when powered off.

When RSTFLTSRW bits (on page 495 of the reference manual) to 10, the LPO clock (configured for 128kHz) for the RESET pin filter clock is set.

The RSTFLTSEL bits can be set to a value from 0  to 31, representing the number of clock cycles the RESET pin transitions are filtered for.

With a 128kHz clock and the RSTFLTSEL bits set to 31, that means that the RESET pin filter time is approximately 2.42us… correct?

If that is correct, it doesn’t seem to be much time for filtering.  PowerPC RESET pin filtering could be set in the millisecond range.

Is there a recommended LPO clock setting for reset pin filtering?  Is 1kHz possible?

[lukaszadrapa]

Hi,

you can select the source of LPO clock in LPOCLKS register:

If you select 1kHz, you can significantly extend the time...

Regards,

Lukas

[ScottKerstein]

Can I assume that the reset values of the registers that are specified in the reference manual are the values after any type of microcontroller reset (i.e. POR, LVD, Watchdog, Software, etc.), or are those values only for POR reset.

Thanks, in advance

Scott

[lukaszadrapa]

If not explicitly mentioned, the reset values are valid for any type of reset. If it is different (typically after POR reset) then it is mentioned like this:

Regards,

Lukas