Which is valid if both DISABLE_PSWITCH bit and AUTO_RESTART bit enabled.

[t-iishii]

Hi community

In i.MX28, if DISABLE_PSWITH bit and AUTO_RESTART bit are enabled,

Which function will work? 

  1) Disables the pswitch pin startup functionality unless the voltage on the pswitch pin goes above the
VDDXTAL pin voltage by a threshold voltage.

  2) Set to one to enable the chip to automatically power up approximately 180 ms after powering down.

Best regards,

Ishii.

[igorpadykov · Accepted solution]

Hi Ishii

seems DISABLE_PSWITH takes priority, as AUTO_RESTART just

gives another way to use DISABLE_PSWITH functionality.

Best regards
igor
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[t-iishii]

Dear igor,

Our customer says that their board will boot up though both condition are enable.

It seems that DISABLE_PSWITCH enable enable is not functioning.

 1) DISABLE_PSWITCH = 1 and AUTO_RESTART = 1

 2) PSWITCH pin voltage < VDDXTAL pin voltage.

Do you know another condition to power up the device?

Our customer design to use DCDC_BATT source only.

Best regards,

Ishii.

[igorpadykov]

Hi Ishii

how customer starts-up board with DCDC_BATT source only design

and disabled PSWITCH .

>Do you know another condition to power up the device?

please check sect.11.3.3 Power-Up Sequence i.MX28 Reference Manual

http://cache.freescale.com/files/dsp/doc/ref_manual/MCIMX28RM.pdf

Best regards
igor

[t-iishii]

Dear igor,

Thank you for your quick response.

I read 11.3 of Reference Manual and have 3 question.

1) How to defined VDDXTAL voltage?

    Who generate VDDXTAL pin output?

2) HW_RTC_PERSISTENT0_AUTO_RESTART bit can be controlled to on/off

    the internal 5-KΩ register between PSWITCH and VDDXTAL?

        If AUTO_RESTART bit is enabled, PSWITCH connected to VDDXTAL by internal register.
        As a result, voltage level would be PSWITCH = VDDXTAL and will be detected MID level.

     Is it correct?

3) MID level of PSWITCH seems less than VDDXTAL, So DISABLE_PSWITCH bit should effect

    only recovery mode function compared with HIGH LEVEL voltage?

Best regards,

Ishii.

[igorpadykov]

Hi Ishii

1.  VDDXTAL is generated internally when processor powered through Battery or +5V.
2.correct
3. from Table 11-1. PSWITCH Input Characteristics i.MX28 RM :
"A MID LEVEL PSWITCH state can be generated by connecting the VDDXTAL
output of the SOC to PSWITCH through a switch."
Customer can check DISABLE_PSWITCH = 1 by applying external voltage to
PSWITCH pin.

Best regards
igor

[t-iishii]

Hello igor

Thank you for your quick response.

I understand to use DISABLE_PSWITCH function to control restart function by applying external voltage,

AUTO_RESTART bit must set to be disabled.

Best regards,

Ishii.

[t-iishii]

Dear igor

Thank you for your support.

I understand that DISABLE_PSWITCH setting is strong than AUTO_RESTART setting.

Best regards,

Ishii