topic Re: imx8mp eMMC interface pull ups in i.MX Processors

imx8mp eMMC interface pull ups

diegoperez — Wed, 20 Oct 2021 12:53:36 GMT

Hi,

I have a question with the eMMC interface and the pull ups, if we look at the EVK schematic there is pull up in SD3_CMD R37 and in SD3_DATA0 R36 but they are marked as not mounted.

Why are they like not mounted?

Are these resistors mounted depending on the eMMC memory? That is, should I put these resistors in my design in case my eMMC needs them?

Thanks and BR.

Re: imx8mp eMMC interface pull ups

nxf63675 — Fri, 22 Oct 2021 00:29:03 GMT

Hi @diegoperez,

This depends on the eMMC that you are using, as the one used on the EVK are not required and they appear as DNP.

For info please look into the hardware developers guide from the i.MX and for the eMMC you select.

https://www.nxp.com/webapp/Download?colCode=IMX8MPHDG

Regards,

Israel.

Re: imx8mp eMMC interface pull ups

diegoperez — Fri, 22 Oct 2021 11:04:28 GMT

Hi,

Thaks for your reply @nxf63675

In my emmc datasheet says this:

So I need 50K as maximun (I am using 1.8V) in all signals, I am thinking to use the internal pull ups of the imx8mp, that in the datasheet says that the maximun value is 49K.

I have a simple question, pull up configuration is associated to the GPIO function or is independent and can be used when USDHC3 peripheral is working with these pads?

Re: imx8mp eMMC interface pull ups

nxf63675 — Mon, 25 Oct 2021 19:52:09 GMT

Hi @diegoperez,

Well, depends on the way you configure your PAD but simply, the answer is yes, as these pins can be used as a GPIO.

Regards,

Israel.

Re: imx8mp eMMC interface pull ups

BiyongSUN — Tue, 26 Oct 2021 07:33:14 GMT

The pull up on data0 and command lines are used for "in case".

In case, there is some hardware layout issue for example need to debug hardware.

add the external pull up can make the ware form better in case layout has issue.

When you debug hardware, you can use the 1 bit mode for emmc. that is why you can see the pull up only on data0.

also suggest you can add one 0 ohm series resistor in the clk "in case" need to debug the hardware for timing issue, which also may be caused by layout sometime. You can adjust that series resistor.

The pad/pin settings are independent as show below picture. no related to GPIO. related to IOMUX.

The GPIO, ADC, SAI are equal.(In blue of the picture). they only take of care of logic "0" or "1"

The pads/pins(silicon ) is in red.