eMMC 5.0 backward compatibility design for picozed based custom board

Question

In previous forum topics, I've been recommended MTFC8GAKAJCN-4M IT (5.0 compliant) as qualified design part. This part is 5.0 compliant and has DS "data strobe" pin added to the interface.

Could you confirm that this "DS" pin specific to eMMC 5.0 protocol can be left floating on a Picozed based custom brd design intended for 4.4.1 operation?

For example, I would use the exact same firmware/BSP setting of default picozed board and the zynq will revert back to 4.4.1 operation without the use of DS.

I think I've seen this case for NXP:

https://community.nxp.com/docs/DOC-332187

If this is not true, do you have HW/SW guides to make the new eMMC work?

Thanks

bhfletcher · Accepted Answer

According to the eMMC datashet, the data strobe is only used in HS400 mode. Since that is not a valid mode in the older devices, it is unused when used in a legacy footprint.

On the v5.0 153-ball eMMC, the DS signal is on pin H5. The PicoZed schematic footprint is based on the larger, footprint compatible 169-ball package, which maps this signal to pin R5. On PicoZed, pin R5/H5 is a no-connect.

When we did our testing with the v5.0 on PicoZed, we used the same hardware platform and BSP settings to test the operation.

Note that Zynq itself is compliant with MMC 3.31.

Bryan