What are the possible reasons for MPC5746C reset

[ssure]

Hi,

we are using MPC5746C and I am seeing that the device is getting reset after twice after power-on i.e., once after 50msec & then after 2secs.

I am seeing a low pulse on the oscilloscope when I probe RESET_N signal in both the reset scenarios.

What could be the possible reasons for the device to reset & how can I identify the root cause for this reset in MPC5746C ?

Also, when I looked into destructive event status register, I am seeing on power on reset flag as TRUE.

I probed Power on reset signal as well but no transitions during this failure scenario.

Regards,

Satya Sudhir

[ssure · Accepted solution]

Hi,

We found that there is a dip in the voltage supply to Microcontroller which is causing the Controller to reset but this reason could be not identified by the registers.

Thanks for your support.

Regards,

Satya Sudhir

[petervlna]

Hi,

What could be the possible reasons for the device to reset & how can I identify the root cause for this reset in MPC5746C ?

For the reset reason you can simply look at RGM module FES and DES registers. There are latched all reset sources.

Also, when I looked into destructive event status register, I am seeing on power on reset flag as TRUE.

which flag? There should be only POR set in DES register after power on reset.

Check the FES and DES after the reset caused by your application.

regards,

Peter

[ssure]

Hi,

I looked into DES register of MC_RGM & below is the snapshot :

I am seeing a low pulse on the reset pin during the reset scenario but not on the PORST_N pin but the status shows Power on Reset in DES register.

Regards,

Satya Sudhir

[petervlna]

Hi,

I looked into DES register of MC_RGM & below is the snapshot :

I am afraid there is no screenshot.

I am seeing a low pulse on the reset pin during the reset scenario but not on the PORST_N pin but the status shows Power on Reset in DES register.

Power on reset bit is set everytime you trigger power on reset.

Are you analyzing and clearing the FES and DES registers after power on reset?

Could you please answer my 2 questions in previous post? Otherwise I am not able to tell you whats happening with your micro.

regards,

Peter

[ssure]

Hi,

I am sorry for the late reply. I have attached the snapshot below in which I connected JTAG and read the register value.

Only POR bit is set which indicates that Power on event has occured but in reality, there is no variation in the input power supply but still we could the controller is resetting after approx., 6 secs.

Also, in FES (Functional Event Status) Register, Self Test completed flag (F_ST_DONE) and F_EXR (External reset event) are set. Which register we need to consider for analyzing the reset issue DES or FES ? and when does F_ST_DONE flag sets ?

Regards,

Satya Sudhir

[ssure]

Hi,

Below is the snapshot of FES Register in which F_ST_DONE (self test completed flag) event is set:

what is the significance of F_ST_DONE event and during the reset scenario, F_POR bit in DES register is set and F_ST_DONE in FES register is set. Does it mean that it is only power on reset or is there any other source?

Regards,

Satya Sudhir