Hi all.
I know that, in terms of card capacity, at last two types of SD Memory Cards are defined:
• Standard Capacity SD Memory Card (SDSC) supporting capacity up to and including 2G bytes.
• High Capacity SD Memory Card (SDHC) supporting capacity more than 2G bytes up to 32G bytes.
Our host cpu is a TI AM1808 (ARM9), and its MMC/SD card controller supports the SD Physical Layer Specification v1.1 as stated in the manufacturer user's guide (SPRUFV8A).
Moreover, the SD Specifications states that,
"Only hosts that are compliant to the Physical Layer Specification Version 2.00 or later can access SDHC. Other hosts fail to initialize SDHC"
(Part 1: Physical Layer Simplified Specification Version 3.01 - May 18, 2010)
Now, this statement seems to be contradicted by a simple experiment on AM1808 EVM board, as described below.
1) on inserting a 1GB SDSC card:
root@am180x-evm:~# mmc0: new high speed SD card at address ed17
mmcblk0: mmc0:ed17 SD01G 982 MiB
mmcblk0: p1
2) Let's use fdisk
root@am180x-evm:~# fdisk -l /dev/mmcblk0
Disk /dev/mmcblk0: 1030 MB, 1030225920 bytes
255 heads, 63 sectors/track, 125 cylinders, total 2012160 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00012e8a
Device Boot Start End Blocks Id System
/dev/mmcblk0p1 63 2008124 1004031 b W95 FAT32
3) Let's read card's content
root@am180x-evm:~# ls /media/mmcblk0p1/
MLO u-boot.bin x-load.bin.ift_for_NAND
flash-uboot.bin uImage
ramdisk.gz ubi.img
AS EXPECTED AM1808 WORKS FINE WITH SDSC.
Now, let's repeat the same sequence on a High Capacity SD card.
4) on inserting a 8GB SDHC card:
root@am180x-evm:~# mmc0: new high speed SDHC card at address 1334
mmcblk0: mmc0:1334 SW08G 7.40 GiB
mmcblk0: p1
5) Let's use fdisk
root@am180x-evm:~# fdisk -l /dev/mmcblk0
Disk /dev/mmcblk0: 7952 MB, 7952400384 bytes
211 heads, 12 sectors/track, 6134 cylinders, total 15532032 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
/dev/mmcblk0p1 8192 15532031 7761920 b W95 FAT32
6) Let's read card's content
root@am180x-evm:~# ls /media/mmcblk0p1/
DCIM myfile.txt
THEN AM1808 WORKS FINE WITH SDHC !
Please, is there anybody who can clarify ?
Best Regards,
Gabriele Filosofi