Using UHS-I bus speeds on SD/MMC card interface

[lpcware]

Content originally posted in LPCWare by salsasepp on Fri May 04 11:31:24 MST 2012
Hi,

I am looking for a powerful microcontroller allowing me to transfer from/to a SD card at near 50 Megabytes per second, i.e. use a UHS-I bus interface at 1.8V signaling. Choices are few - I may be reaching for the stars here.

However, the LPC43xx seems to be capable:
1) user manual says "SD spec version 3.0 supported" -> check, 3.01 is the current spec defining UHS-I
2) user manual details the UHS-I register with 1.8V/3.3V buffer voltage switching and DDR mode on/off -> looking good
3) datasheet says "SD card clock typ. 40MHz, max. <tbd>" -> that's a maybe, 50MHz might enable UHS-I DDR50 mode

I checked the schematics of the Hitex and the NGX Tech LPC43xx evaluation boards, but both operate the SD card slot at 3.3V only. This precludes the use of any of the 1.8V signaling modes (e.g. DDR50), which alone would enable operation at more than 25 Megabytes/second.

Questions:
a) Does anyone know of an eval board that has 1.8/3.3V voltage switching for the SD card? I believe that would mean having level translators for the data bits and switchable card power, somehow connected to the SD_VOLT[2:0] pins.
b) Has anyone successfully used UHS-I modes with the LPC43xx?

Thank you,
Stefan.

[lpcware]

Content originally posted in LPCWare by bowerymarc on Wed Apr 24 12:59:05 MST 2013

+1 for that wishlist.

[lpcware]

Content originally posted in LPCWare by salsasepp on Tue Jun 05 07:24:58 MST 2012
Additional information: Bury the above dream. Any UHS-I bus speeds faster than "default speed" (i.e. requiring 1.8V signaling or clock speeds of 50MHz or more) are not supported.

I got answer from NXP support: UHS-I DDR50 mode is a "no".
Looking across at the LPC18xx, I see that somewhere after revision 1.1 of the user manual, the UHS_REG 0x074 went "reserved". I guess that with the next LPC43xx user manual revision after "Rev 1", the same will happen there. I knew before what a "preliminary user manual" and an "objective datasheet" is...

Wishlist:
- UHS-I bus speeds and 1.8V signaling on a Cortex M3 or M4 microcontroller. All the way.

[lpcware]

Content originally posted in LPCWare by salsasepp on Fri May 04 23:52:41 MST 2012
Clarification:

Actually, the SD card operating voltage (2.7V - 3.6V) does not change when the signaling levels are switched. One just needs fast level translators with card-side 1.8V/3.3V switching (the ST6G3244ME or the Toshiba T3GF3WBG chips are built for this).