How Much Do You Know about SD Card
As a new memory device, an SD card came into our life and brought us much convenience. To be honest, SD cards have a wide application range; they can be used in digital cameras, mobile phones, MP3/4 players, game machines, etc. As technology is developing, SD card technology has also taken a big step forward.
You may not have heard of MMC (Multimedia Card) before. But in fact, SD card technology has been developed on the basis of the MMC format. There is not much difference in the size of the SD card and MMC. The length and width of an SD card are basically the same as that of an MMC. Little difference can be found in thickness. SD card is only slightly thicker than MMC. MMC can be used in an SD card supported device, while an SD card can’t be applied to a former MMC-supported device.
SD card enjoys a weight of only 2 grams, but it features many fascinating merits, such as large capacity, fast data transfer rate, great flexibility, and good security. Adopting a very efficient data compression method, an SD card is able to provide sufficient space for multimedia data. SD card supports three kinds of transmission modes: that are SPI mode (separate serial input and serial output), 1-bit SD mode (separate command and data channel and a unique transmission format), and 4-bit SD mode (using extra pins and some re-set pins and supporting four-bit parallel transmission).
All in all, provided with the characteristics of small size, low power consumption, and erasable and nonvolatile ability, SD cards are widely used in various electronic products. Its application range is growing, especially in recent years, with the obvious decrease in price and increase in capacity. Just because of that, you may see or hear SD card related problems quite often, such as how to retrieve files from SD card and how to deal with the SD card not accessible issue. Here, we’ll talk something about SD card data read and write.
SD Card Data Read and Write
There exist two modes in the reading and writing of SD card data: Single Block Mode and Multiple Block Mode.
Single Block Mode: the host will read and write a data block according to the pre-defined length. A 16-bit CRC check code will be generated by the transmission module and the receiving terminal will check by using this check code. Unaligned access is not allowed, so each block must be located within a single physical sector.
Multiple Block Mode: the host can read multiple data blocks (of the same length) at the same time; it may read data from or write data into contiguous memory addresses according to the address in command. The operation will be ended by a stop transmission command.
Please keep reading the following content to know how to read a data block from and write a data block into an SD card.
Read a data block from an SD card: this whole process is very easy. The host gives a “READ_SINGLE_BLOCK” command and sets the starting byte address as a parameter. Then, SD card will check this address and send an R1 command in response to that action. If this kind of SD medium read/write operation has been finished, a starting data token, a fixed number of data and the two bytes of CRC – 16 checksum will be sent. If SD card hardware failure or read/write failure occurs, any one of them will not be sent. Instead, an error token will be sent to stop data transmission.
Write a data block into an SD card: this process is similar to the data block reading process. Initialize the write operation by sending a “WRITE_BLOCK” command. Then, the SD card will respond in the R1 command responding format. If the command gets a response, it indicates the operation can be carried out. So the host will send a starting data token, a fixed number of data, and the two bytes of CRC – 16 checksum and then end this procedure. Now, the SD card will send back a data response command to indicate whether the data waiting to be written into the SD card are acceptable or not to determine the subsequent operations.
Why SD Card Cannot Be Accessed
Compared to an internal computer hard drive, an SD card is relatively weak. Since the SD card is featured with great portability, it can be taken out and moved from one place to another easily. This increases the possibility to fall victim to a lot of factors, such as dust or oil stain, unstable voltage, squeezed slot, rusty or bending slot metal wire, and virus infection. Besides, if the SD card has been improperly formatted or damaged physically, we’re also not able to read data in it.
#1. Dust or oil stain: As some users may not have protected the SD card chip well every time when they take it out from the original device, dust or oil stain will occur and accumulate on the surface, making the SD card not accessible on any device or computer.
In this case, users can stare at the surface of the SD card chip carefully to see whether there is much dust and whether the metal region is dim or covered by spots. If it is a fact, users need to wipe the surface of the SD card chip gently by using the cotton that has been moistened with alcohol or water.
#2. Unstable voltage: A high-quality SD card has a high requirement in power supply. So if the battery used in users’ SD card devices is not original, but an inferior product, users will meet data access failure.
At this time, users are strongly suggested to change the battery to an original or superior one. If it still fails, users probably ought to recover data from inaccessible SD cards with the help of professional recovery companies or programs.
#3. Squeezed slot: For some SD card supported equipment, especially the slim machine, the slot design is very clever. If a non-original or non-formal battery is used, the slot may be squeezed since the thickness exceeds a certain standard.
Now, users can choose to adjust the slot carefully or change the battery for the device.
#4. Rusty or bending slot metal wire: The internal data transmission is mostly done by the metal wire in the slot. Since the majority of devices are hot-swappable, the rusty or bending metal wire problem may occur frequently.
If users suspect this is the reason that leads to SD card not accessible, they can make the slot facing the sun and observe whether the metal wire contacts are at the same height. If they’re not stay at the same height, then this problem can be confirmed. In this situation, users can try to use a needle to adjust the metal wire height.
#5. Virus infection: Virus is regarded as one of the biggest threats to data saved in multimedia storage devices. Users can easily get their SD card infected during data transmission with other devices. Therefore, users can’t be too careful when using the device SD card, which has important data stored in it.
Users can use an antivirus program to check whether their card has been attacked by a virus. But users should remember that they shouldn’t kill the virus or format the SD card until they retrieve all files from SD card successfully.
No matter what the reason is for SD card not accessible and data loss problems (it doesn’t matter if the SD card is improperly formatted or damaged physically), the first thing users will think about is absolutely how to retrieve files from SD card. We’re sure that users will care much more about data rather than the SD card that stores them in most cases. Certainly, this is reasonable and the right thing to do.
Retrieve Files from SD Card That Is Inaccessible
Please read the following phenomena that indicate SD card damage to see whether you are familiar with them or not. And corresponding steps to recover data from inaccessible SD card will be given later to help you get rid of the SD card inaccessible disaster.
>> Phenomenon 1: After you connect your SD card to a computer and click on the drive that stands for your SD card, you get the prompt message shown below. (We can confirm that this problem is caused by file system failure by just reading the information on the prompt window)
>> Phenomenon 2: you’re asked to format the SD card that you’ve connected to a computer through a data line when you try to open it. It’s obvious that only after you allow formatting the card by clicking on “Format disk”, you’re able to use the SD card again to manage data and save new files. On the contrary, if you tap “Cancel” instead, you’ll find the SD card not accessible to you.
>> Phenomenon 3: you may also see the “*:\ is not accessible” prompt when trying to access the SD card on a computer. At this time, you can only click “OK” to close the prompt window, but that problem still exists and you’re still not able to see any files in the SD card.
No matter which situation you’re in face of, the only right choice at that very moment when you see those error messages is to seek methods for retrieving files from an SD card without wasting a minute.
In fact, the reason why those phenomena appear is that the SD card has been damaged whether due to accidental formatting or other operations. Thus, we plan to offer a good solution to helping users get data back from formatted SD card so as to get rid of the SD card inaccessible problem. That is to employ MiniTool Power Data Recovery right after disaster appeared.
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Step Guide to Recover Data from Inaccessible SD Card
From the beginning, you should download and install MiniTool Power Data Recovery Free on your computer. The free edition enables you to scan files from an inaccessible SD card and recover no more than 1GB of files.
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After this, connect the SD card to your computer and launch the software. You should ensure that the SD card is detected by the software. This software can restore files lost in various situations, including partition loss, file system corruption, device formatted, and more. Thus, you can scan the inaccessible SD card to see if the stored files can be found. Hover your mouse over the partition of the SD card and click Scan. Alternatively, you can change to the Devices tab to scan the SD card device.
The scan process may last for a few minutes, depending on the number of files and the capacity of your SD card. You can browse the found files during the scan process but do not interrupt the process for the best scan result.
On the result page, you are advised to use the embedded features to pinpoint the required files.
- Filter: Set filter conditions, such as file size, file type, file category, and file last modified date to filter out unwanted files.
- Type: Change to the Type tab to check files that are sorted by their types and file formats.
- Search: Locate the target file by inputting the file name and pressing the Enter key.
- Preview: Check the file content of the chosen file before saving it by double-clicking on the file or selecting it and clicking the Preview button.
With the above features, you can quickly find the required files. Afterward, tick them and click the Save button. You need to choose a restoration path that is different from the original one. Saving files to the original path might overwrite the data and cause data recovery to fail.
This is a complete data recovery guide when you encounter the SD card not accessible with MiniTool Power Data Recovery. As we mentioned in the above content, MiniTool Power Data Recovery Free only can recover 1GB of files from the device. If you want to break the limit to recover more files, you should get an advanced edition. MiniTool Power Data Recovery contains several editions. You can visit this page to choose one edition that works on your situation best.
Things You Should Pay Attention to
As we have mentioned before, an SD card is easy to fall victim to a lot of reasons and all data in it may be lost, making users suffer a lot. Therefore, we’d like to talk about something that users should pay enough attention to when they’re using an SD card. Otherwise, the serious data loss in the SD card may be a terrible nightmare.
1. Try to look through the photos you have taken with digital devices on a computer after taking out the SD card and connecting it to the computer properly. Of course, you also need to do so if you’re planning to modify the photos. The direct modification of the SD card increases the possibility of getting your SD card crashed. What’s more, the modification of a lot of pictures may lead to SD Card “paralysis”.
2. If the device that contains an SD card is getting stuck or crashed, this indicates that there’s serious trouble with your SD card. You may see a prompt asking you to format the SD card in this situation. But remember, please don’t allow doing so until you have recovered data from inaccessible SD card successfully. After that, you can choose to format the SD card for further use. Anyway, we don’t suggest users save important files into that SD card again since the same problem is likely to occur every now and then.
3. When you’re selecting an SD card, please try to choose genuine products and avoid getting pirated and counterfeit products with an amazingly low price or beautiful appearance. And the situation is the same when you’re searching for a good card reader.
4. Please don’t feel troublesome to plug in or unplug the mobile SD card properly into the computer in order to manage data in it well. Instead, you should do exactly as required to connect the SD card safely.
5. If the drive letter loss, data inaccessible, messy codes, or capacity turning into zero problems occur after you connect the SD card to the computer, please don’t take any action to try to fix the problem. The first thing you should do is, of course, figure out ways to retrieve files from SD card safely. Then, you can do whatever you want to do.
Summary
SD cards are vulnerable to encountering various problems. If you are troubled by the SD card not accessible issue, please first rescue your files from the device to avoid secondary damage to the original data. After that, you can carry out measures to fix the SD card error.
If you have any issues in recovering files from the SD card with MiniTool Power Data Recovery, please feel free to let us know via [email protected].
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