LPC54608 Reset switch issues

[germano]

Hi! I'm working with a custom board based on a LPC54608.

Generally everything works fine, however, sometimes when you press the reset button. The microcontroller remains frozen and does not start, and I need to disconnect the power and reconnect it to correct the problem.

My reset circuit is shown in the figure below.

Is it necessary to consider something else to restet the microcontroller?

[jeremyzhou]

Hi germano,

Thank you for your interest in NXP Semiconductor products and for the opportunity to serve you.
to be honest, according to the schematic, it's hard to find the cause of the phenomenon.
I'd like to know the mean of 'microcontroller remains frozen and does not start', does the external crystal Y1 can start up successful?
Maybe you should confirm whether the MCU enter the ISP mode.
Have a great day,
TIC

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[microcris]

In my case, the  MCU enters the ISP mode.

It "randomly switches" between ISP0, ISP1 and ISP2. Since those pins are connected to EMC bus, It depends from whom is low at the reset moment. 

And, again in my case, it happens more often when I preform two consecutive resets because I start a full sdram consistency scan immediately after a reset.

Thank you for pointing out the possibility of entering in ISP without external command.

[germano]

Hi jeremyzhou,

'microcontroller remains frozen and does not start' means that the flash program doesn' start.

The cristyal is working fine, at the same frequency always.

On ISP select pins I copied the circuit of LPCXpresso54608, but I don't know how to chek if the MCU is on ISP Mode or not.

Anyway, is there any way to ensure that the MCU does not initialize in ISP mode?

Edit: I found that the issue is more frecuent when the reset switch is pressed while MCU is writing on SDRAM

[jeremyzhou]

Hi germano,

Thanks for your reply.
According to your attachment, I find that the PIO0_4 (ISP_0), PIO0_5 (ISP_1) and PIO0_6 (ISP_2) will be used as the EMC data pins, to eliminate the potential interference of the status of these data pins, add two pull-up resistors to PIO0_5 and PIO0_6, just did with the PIO0_4, or assert the CRP_ISP_DISABLE_PIN bit to disable the ability to enter ISP mode using the ISP pin.

Have a great day,
TIC

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[germano]

Thank you!

The pull up resistors didn't work, but I fix the issue by writing OTP to disable ISP Mode.

[jeremyzhou]

Hi germano,

Thanks for your reply.
Glad to hear that the issue is resolved:smileyhappy:.

Have a great day,
TIC

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[microcris]

I have the same problem with a LPC54628.

It seems to happen when two resets are issued in a very short time.