Sd3.0-host-ahb-emmc4.4-usersguide-ver5.9-jan11-10.pdf -

Just spent some time with an older but gold reference doc: . Even though it's dated, there are some architectural notes that still apply to legacy eMMC bring-ups.

Digging into sd3.0-host-ahb-emmc4.4-usersguide-ver5.9-jan11-10.pdf – Key Takeaways sd3.0-host-ahb-emmc4.4-usersguide-ver5.9-jan11-10.pdf

This appears to cover an AHB-based SD/MMC host controller (SD 3.0 spec) talking to eMMC 4.4 devices. Likely from an SoC vendor's IP block (maybe Synopsys or a proprietary ARM-based design). Just spent some time with an older but gold reference doc: