topic Re: KL02 SWD_DIO or SWD_CLK in Kinetis Microcontrollers

KL02 SWD_DIO or SWD_CLK

patrickirwin — Fri, 09 Aug 2013 18:32:36 GMT

We are currently using MKL02Z16VFG4 (16 pin device) in a new
design. In this design we are using all
of the pins except for pin 16 (PTA2/SWD_DIO) and pin 14 (PTA0/SWD_CLK). After programming, we need to use one of
these pins to drive an N-Channel MOSFET, which is being used as a switch. The N-Channel MOSFET has a pull down 10K ohm
resistor from its gate to ground.

Which pin should we be using?

Thanks

Pat

Re: KL02 SWD_DIO or SWD_CLK

martynhunt — Fri, 09 Aug 2013 20:02:37 GMT

Hi Pat,

Both pins can be used. The differences between the two pins are:

PTA0 has interrupt requests; PTA2 does not.

PTA0 does not have an internal pull-up. PTA2 does.

So if you need to add an interrupt driven input later, use PTA2 for switching the MOSFET to leave PTA0 available.

Best regards,

Martyn

Re: KL02 SWD_DIO or SWD_CLK

patrickirwin — Fri, 16 Aug 2013 18:43:23 GMT

Martyn,

Does the PTA2/SWD_DIO require a pull-up? The IAR I-JET states when using J-TAG “This pin should be pulled up on target”.

While for PT0/SWD_CLK pin says that when using J-TAG “It is recommended that this pin is pulled to a defined state on target board”.

If we need a pull-down to the MOSFET, we should use the PTA2/SWD_DIO. We are using J-TAG for programming.

Thanks

Pat

Re: KL02 SWD_DIO or SWD_CLK

martynhunt — Mon, 19 Aug 2013 14:36:49 GMT

Hi Pat,

On reset the KL02 enables a pull-up on PTA2/SWD_DIO, and a pull-down on PTA0/SWD_CLK. Therefore, until you change the mux and/or pull-up/down settings in your code, PTA0 & PTA2 are set correctly for programming.

Also, the KL02 does not feature JTAG. All programming/debugging is performed via SWD (Serial Wire Debug) and your IAR I-JET is capable of programming/debugging over SWD.

Best regards,

Martyn

Re: KL02 SWD_DIO or SWD_CLK

patrickirwin — Mon, 19 Aug 2013 15:01:26 GMT

Martyn,

Thanks for your help.

Pat