Table of Contents

Secure Storage

There are two secure storage areas you may find useful: the configuration storage area and the one-time programmable storage area.

Configuration Storage

On SC20260 (and SC20100), there is 128 KByte secure storage area is organized as 4096 blocks of 32 bytes each.

On SC13048 there is 8KB secure storage, organized as 256 blocks of 32 bytes each.

Configuration storage can be erased and modified. Performing an erase all in TinyCLR Config will wipe out this area. As this area is comprised of a single sector of flash memory, only the whole storage area can be erased. Partial erases are not possible.

Tip

Needed NuGets: GHIElectronics.TinyCLR.Core, GHIElectronics.TinyCLR.Devices.SecureStorage

const uint STORAGE_SIZE = 32 * 1024;
var configStorage = new SecureStorageController(SecureStorage.Configuration);
var data = new byte[STORAGE_SIZE];

Debug.WriteLine("Configuration storage total size: " +
    configStorage.TotalSize.ToString() + " bytes.");

Debug.WriteLine("Configuration storage block size: " +
    configStorage.BlockSize.ToString() + " bytes.");

Debug.WriteLine("Checking if blank. . .");
var isBlank = true;

for (uint block = 0; block < configStorage.TotalSize / configStorage.BlockSize; block++) {
    if (!configStorage.IsBlank(block)) isBlank = false;
}

if (isBlank) {
    Debug.WriteLine("Configuration storage area is blank.");
}
else {
    Debug.WriteLine("Erasing entire configuration storage area...");
    configStorage.Erase();
}

Debug.WriteLine("Filling buffer...");

for (var i = 0; i < data.Length; i++) {
    data[i] = (byte)(i % 255);
}

Debug.WriteLine("Writing buffer...");
var dataBlock = new byte[configStorage.BlockSize];

for (uint block = 0; block < data.Length / configStorage.BlockSize; block++) {
    Array.Copy(data, (int)(block * configStorage.BlockSize), dataBlock, 0,
        (int)(configStorage.BlockSize));

    configStorage.Write(block, dataBlock);
}

Debug.WriteLine("Comparing buffer...");

for (uint block = 0; block < data.Length / configStorage.BlockSize; block++) {
    for (var byteIndex = 0; byteIndex < configStorage.BlockSize; byteIndex++) {
        configStorage.Read(block, dataBlock);

        if (data[block * configStorage.BlockSize + byteIndex] != dataBlock[byteIndex]) {
            Debug.WriteLine("Configuration storage data is corrupted!");
            Thread.Sleep(Timeout.Infinite);
        }
    }
}

Debug.WriteLine("Configuration storage is good to go!!!");

One Time Programmable Area

Note

If all 32 bytes of any OTP flash block contain 0xFF, the block is considered unused. If you write only 0xFF to the contents of a block, the block will be regarded as unused and you will be able to rewrite the block.

The one time programmable (OTP) secure flash region is organized into 2048 blocks on SC20260 (or SC20100), and 64 blocks on SC13048 of 32 bytes each. Once you write to a block, that block can be read but never changed.

There is no way to modify written data. Erasing the entire device Erase All in TinyCLR Config will not erase or modify this area.

The API for OTP storage is the same as for the configuration storage area, except that instantiation takes a different argument and the Erase method is disabled.

OTP secure storage is instantiated as follows:

var otpStorage = new SecureStorageController(SecureStorage.Otp);
Note

SC13048 allows write one time on each block, even data all is 0xFF.

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