Schematic Checklist – eMMC DAT Pull-Ups

[mlarkin]

Are the pull-ups on the eMMC DAT signals actually mandatory as suggested per OSD32MP15x Schematic Checklist – Octavo Systems, if the eMMC part has internal pull-ups on the DAT signals?

Looking at the schematics for the STM32MP1 MB1263 (daughter board for eval), they do not have pull-ups on those signals and the eMMC listed in the schematic has internal pull-ups.

Can you provide clarification on if these are needed as it has impact on device trees?

[Neeraj Dantu]

mlarkin,

The eMMC specification requires pull-ups on the interface signals. STM32MP1 I/Os have internal pull-ups that can be activated in bootloaders. For ROM code stage, only D0, CMD and CLK are used. So, EV1 includes pull-ups on these pins. The pull-ups on other data signals are activated in TF-A and the interface is switched from 1 bit to 8 bit interface according to specification in the device tree.

You can either populate the reduced number of pull-ups as in the EV1 schematics and activate the remaining pull-ups in device tree or populate all pull-ups and exclude pull-up configuration in device tree.

Best,
Neeraj

[Author]

Posts