Kinetis MK10, pin state after reset, chip unprogrammed

[retocavelti]

Hello,

for a pre test i need to know following:

i have a MK10DN512VLK10, unprogrammed, but with power supply of 3.3V. External signals of 3.3V are connected to some pin of the microcontroller.

How can i be sure, that none of these signal can damage the unprogrammed but supplied microcontroller?

In the datasheet i can read, that the mux bits of PORTx_PCRn are undefined after reset. So some of the pins of the micro can randomly be configured as outputs (e.g. SPI CS).

So my question is, if this pins also act as outputs or are they only configured as outputs but are still high impendance. Where in the datasheet can i find an answer? Could it be that only after enabling the clock to the modules (e.g. SPI) the pins act as configured?

Best regards.

r.c.

[Jorge_Gonzalez]

Hello Reto Cavelti:

In short: as long as the MCU is powered and you consider the pins maximum input voltage ratings then there is no problem in connecting the pins to external signals. You can check the maximum ratings in the datasheet.

Here is the situation and some points to clarify:

- All Digital IO pins (except for JTAG related pins) default to Disabled, which means high-impedance.

- Pins with analog functions default to their analog functionality.

- The MUX field in the register PORTx_PCRn is undefined at reset because some digital pins as JTAG/EzPort and NMI pins default to that particular functionality instead of disabled, but undefined does not mean that pins are randomly configured after reset.

You could get a better understanding of this by looking at the Signal Multiplexing table in the chapter K10 Signal Multiplexing and Pin Assignments of the Reference Manual.

I hope this helps.

:smileyinfo: NOTE: Datasheet and Reference Manual are separate documents. You can get them from the product page -> Documentation tab:

K10_100 |Kinetis K10 100 MHz MCUs|Freescale

Regards!,
Jorge Gonzalez

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[retocavelti]

Hello Jorge,

Thank you for clarifying this issue.

regards, Reto.