See eMMC spec for details, you can download it from JEDEC after free registration.Ī list of some manufacturer IDs can be found here: Also, the year code of the MMC CID is only 4-bit (specifically (year-1997) mod 16), so to interpret it correctly you need to know which version of the standard is used (obtained from ext_csd). Note that (e)MMC and SD have different CID structures and different manufacturer ID registries! So when cataloguing CIDs be sure to include the device type (found in sysfs attribute ‘type’). Hope you find this useful! Maybe I’ll get around to coding one for the CSD in the future. I won’t warrant the below decoder as being bug free, but it’s free so give it a whirl! If you want a full-screen one, so you can use it side-by-side and compare two separate CIDs, try this “framed” wrapper here. Please note, while the code below works using the Javascript of your browser, I have no prior Javascript coding until today, with much help from Google searches and W3schools. I used this reference by Sandisk for the data field lengths and types. Unfortunately, I haven’t seen a large CID database online, nor have I seen a CID decoder that will decode the hex string into the component parts (some BCD, some ASCII, others Unsigned Int or best as Hex), so I went on a journey to code one up for CID. By comparing some cards that you own with the known signatures, you can have some reassurance whether your cards are similar, or genuine. By running Chrubuntu, getting the CID or CSD data from a card is as simple as: cat /sys/block/mmcblk1/device/cidĮt voila! You will be rewarded with a hexadecimal string with the data in it. Under the Chromebook, the SD reader slot on the side is directly connected to the SD bus of the ARM CPU and is not a USB based reader. I am aware that it was possible to do this via the SD Card Shield and Arduino, but since I have a Chromebook, things got really easy. These can only be accessed directly via hardware and not via most card readers. There is also another called the CSD or Card Specific Data Register. One is known as the CID, short for Card Identification Register. SD cards, along with their “counterparts” mini and microSD cards, all contain manufacturer defined information in a set of registers. Buying flash memory from poorly reputed places, such as Chinese computer markets, and online auction sites is an often known way to collect BAD flash memory cards that fall short on performance, longevity and data security.
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