![]() The unique identifier of the memory card is the CID number. Programming can be done with the CID value. The card model and controller will determine the CID value, so the command used to read it will differ depending on which manufacturer the card is manufactured. The command must also be sent to the vendor-specific register of the card, which cannot be accessed by the USB bus. To read the CID value of a Secure Digital card, however, you will need to issue a vendor command to the controller. The Universal Serial Bus (USB) can be used to read the CID value on a Secure Digital card. This method is available.Ĭommon questions include how to read or write a CID value to the read-only memory space of a Secure Digital card (either microSD or SD). There are situations when content owners might want to modify CID values to conform to their IP (Intellectual Property). It cannot be changed, duplicated, or modified by any user. The CID value is stored in Read Only Memory (ROM). It is done during the card creation stage. The manufacturing process includes the writing of the CID value. ![]() It is used to identify the card and verify its authenticity. It is usually a 16-digit number that is unique to each card. It is stored in the card’s read-only memory and used to track card usage and performance. This article provides a basic overview of how to read and write CID values from a Secure Digital memory card.ĬID numbers, also known as Card ID numbers, are unique identifiers assigned to Secure Digital memory cards. There are many theories on the internet, but there are not many clear answers. We include the CID data in our SD card reviews so you may compare it with your cards.The reading and writing CID values to microSD cards is still a mystery. The CID information can be helpful in identifying counterfeit memory cards. How can I use the information from the CID? CompanyĪgfaPhoto, Delkin, Integral, Lexar, Patriot, PNY, Polaroid, Sony, Verbatim ![]() For example, PNY cards have been found with 0x000028 and BE (Lexar) or 0x000027 and PH (Phison). Many card brands are produced by OEM suppliers, and the MID and OEMID may reflect this, or in some cases they appear to show the producer of the card controller. The following list was compiled by reading the CID on numerous SD cards. They consider this information confidential so an official list is not published. Manufacturer ID (MID) are assigned by the SD Assoication (SD-3C LLC). * these are the attribute titles used for the card in Linuxįor more information, refer to the SD Association Simplified Specifications. Manufacture date is stored in the form yym (offset from 2000)ħ bit code used for checking errors in the card register This 32 bit field is intended to be read as an unsigned integer The PRV can also be found by using the hwrev and fwrev, where x=hwrev and y=fwrev Identifies the card OEM and/or the card contents. The following information is stored in the CID: Name To view the CID, the command is cat /sys/block/mmcblk0/device/cid (the exact location may be different) What information is in the CID? Under this location you will see several attributes available that include the CID and CSD registers and the information inside it. Insert the card and look under /sys/block/mmcblk0/device/ (this location may change depending on your platform, it may be mmcblk1 or in a different location). With Linux, reading the internal SD card information is simple. Not all computers with built-in card slots will work, some internal card readers are connected through a USB bus.Īssuming you have the proper hardware, there are several methods you can use to get the card information. This will not work through a USB card reader because the command to retrieve the card information is intercepted and not understood by card readers. Card readers in laptops are usually connected directly through the PCI bus (or IDE bus). One way to read the CID is to use a laptop with an SD card slot. (According to SD card specification the information is only to be written once, however if a card does not conform to the specification this information could be changed!) How to read the CID from an SD card The CID register is set when the card is manufactured and cannot be changed after it is set. One of these is the Card Identification (CID) Register, a 16 byte code that contains information that uniquely identifies the SD card, including the card serial number (PSN), manufacturer ID number (MID) and manufacture date (MDT). Information about an SD card is encoded in its internal card registries.
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