Kinetis MicrocontrollersのトピックRe: SPI drive strength and slew rate

SPI drive strength and slew rate

MikeTheFox — Wed, 16 Sep 2020 14:09:27 GMT

Refer to MCU: MK66FN2M0VMD18

Refer to datasheet: https://www.nxp.com/docs/en/data-sheet/K66P144M180SF5V2.pdf

Refer to ref. manual: https://www.nxp.com/docs/en/reference-manual/K66P144M180SF5RMV2.pdf

Question 1: In the datasheet section 2.1 you can read that slew rate disabled and normal drive strength, what is the meaning of disabled (fast or slow) and normal (high or low) ?

Question 2: I'am using PTD1 pin as SPI clock line. The drive strength enable control can not be changed for this specific pin.acc. to the reference manual section 11.2.2. So what is the default drive strength for this pin (high or low) ?

Re: SPI drive strength and slew rate

gusarambula — Fri, 18 Sep 2020 01:53:20 GMT

Hello MikeTheFox,

Regarding your fist question, it is my understanding that normal in regards as of drive strength refers to the out of reset condition, which would be low drive strength or DSE (Drive Strength Enable) disabled, as shown on Table 11-2 of the K66 Reference Manual. I will confirm this and provide feedback to our documentation team as “normal” may not be the best way to specify this configuration.

The Slew Rate disabled (SRE = 0) would result in a fast slew rate configuration on the corresponding pin.

As for your second question, since the drove strength control is disabled it is my understanding that the corresponding drive strength would be setup to low. I will also confirm this and I will let you know as soon as I have more information.

Regards,
Gustavo

Re: SPI drive strength and slew rate

MikeTheFox — Thu, 24 Sep 2020 07:12:38 GMT

Looking forward to hearing from you soon regarding the confirmation of the drive strength (high/low) and the slew rate (fast/slow).

Re: SPI drive strength and slew rate

gusarambula — Thu, 24 Sep 2020 19:01:56 GMT

Hello MikeTheFox,

I'm still waiting for confirmation on this information. I will let you know as soon as I receive an answer.

Regards,
Gustavo

Re: SPI drive strength and slew rate

gusarambula — Mon, 28 Sep 2020 15:33:47 GMT

Hello MikeTheFox,

My apologies for the delay.

I confirmed that by “normal” they are indeed referring to DSE=0 or “low drive strength”. When a pin does not have a drive strength configuration the drive strength would be a low drive strength unless specified otherwise.

Regards,
Gustavo

Re: SPI drive strength and slew rate

MikeTheFox — Tue, 27 Oct 2020 12:44:56 GMT

Hi, thanks for your answer. I assume you are going to update datasheet and relevant documentation.

Follow up question 1: What is the default setting of the DSE bit and SRE bit after hardware reset (refer to Pin Control Register) ?

Follow up question 2: Where can we found numbers for rise time and fall time depending of DSE and SRE bit settings ?