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RESETb/PTA20 on KL15 as "GPIO"?

Question asked by Wolfgang Wegner on Nov 24, 2014
Latest reply on Nov 25, 2014 by Jorge_Gonzalez

Hi,

 

I am trying to get a workaround for the following problem:
- KL15Z128 MCU
- bootloader uses SRCM_SRS1 & RCM_SRS1_SW_MASK as criterion to stay in bootloader/update mode
- watchdog is unused/disabled

- I need to reset the MCU from the application while restarting (not staying in bootloader/update mode), so
  SW reset can not be used for this.

 

As I have a rather large capacitor and pull-up connected to RESETb/PTA20
I thought about setting PTA20 low as a GPIO and then switch it back to
RESETb function to let the MCU reset itself, but this does not work. This
is my code:

PORT_PCR_REG(PORTA_BASE_PTR, 20) = PORT_PCR_MUX(1);
GPIOA_PDDR |= (1 << 20);
GPIOA_PCOR = 1 << 20;
delay_ticks(2);
PORT_PCR_REG(PORTA_BASE_PTR, 20) = PORT_PCR_MUX(0);

 

 

There is no low pulse on PTA20 and when single-stepping through the
code, I can see PORTA_PCR20, GPIOA_PDDR and GPIOA_PDOR

being correctly set, but GPIOA_PDIR always reads '1' in bit 20.

 

From the data sheet I see no limitation in PTA20 GPIO functionality,
but to me it seems that this pin is input-only in hardware.
Did anybody else try this yet and can share their experience?

 

Best regards,
Wolfgang

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