i.mx28 and RESETN problem.

[fear_nada]

Hi all,

I have problem with RESETN and i.mx28. I use VDD5V power supply only.

i use external watchdog IC for generate RESETN signal. For test i am not refresh wdg and after some good reboots(10-50) my i.mx28 go to hang state.

vddxtal - 0.97

dcdc_vddio_3v3 - 3.0

vdd4p2 - 0.3V

dcdc_vddd_1v2 - 1.0V

dcdc_vdda_1v8 - 0.96

vdd5v 4.95v

Clock on 24Mhz - are present.

and only one way to out from this hang state - remove power and apply it again.

I use boot from NAND flash and then "hang" happend i cant see any chip selects signal GPMI_CS0.

and in debug serial not any debug info.

Is this possible that internal bootloader are "hang"? Where i can see bootloader code for understand why boot stopped.

Is this possible that internal LDO (VDD5V to VDD4P2) go to current limit state? But why reasserting RESETN not restore it.

On my board i supply only DDR, NAND and i.mx from internal i.mx power sources.

Why on i.mx28 EVK added MOSFET for break VDD5V then reset button pressed?

[igorpadykov]

Hi fear

recommended way to do RESETN is to remove VDD5V

(as i.mx28 EVK is doind  with MOSFET), that is as at

power-up. Otherwise one can encounter with weird problems,

for example VDD4P2 is disabled at reset according to sect.

11.12.9 DC-DC Converter 4.2V Control Register

(HW_POWER_DCDC4P2) , bit ENABLE_4P2 =0 MCIMX28RM

Best regards

chip

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