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

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by salsasepp on Fri May 04 11:31:24 MST 2012

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.

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,