Schematic Checklist – eMMC DAT Pull-Ups
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- This topic has 1 reply, 2 voices, and was last updated 2 years, 5 months ago by
Neeraj Dantu.
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- May 9, 2022 at 7:26 am #12384
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?
- May 10, 2022 at 10:40 am #12387
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
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