barCodeScanningGun/arduinoLibrary/rc522/MFRC522/doc/PICCMemoryLayout.md

Memory Layout of common PICCs

To read and write from MIFARE PICCs, the MIFARE protocol is used after the PICC has been selected.

Datasheet References

The MIFARE Classic chips and protocol is described in the datasheets:

• 1K: https://www.mouser.com/ds/2/302/MF1S503x-89574.pdf
• 4K: https://datasheet.octopart.com/MF1S7035DA4,118-NXP-Semiconductors-datasheet-11046188.pdf
• Mini: http://www.idcardmarket.com/download/mifare_S20_datasheet.pdf

The MIFARE Ultralight chip and protocol is described in the datasheets:

• Ultralight: https://www.nxp.com/docs/en/data-sheet/MF0ICU1.pdf
• Ultralight C: https://www.nxp.com/docs/en/data-sheet/MF0ICU2_SDS_32.pdf

MIFARE Classic 1K (MF1S503x)

Has 16 sectors4 blocks/sector16 bytes/block = 1024 bytes.

The blocks are numbered 0-63.
Block 3 in each sector is the Sector Trailer. See https://www.mouser.com/ds/2/302/MF1S503x-89574.pdf sections 8.6 and 8.7:
    Bytes 0-5:   Key A
    Bytes 6-8:   Access Bits
    Bytes 9:     User data
    Bytes 10-15: Key B (or user data)
Block 0 is read-only manufacturer data.
To access a block, an authentication using a key from the block's sector must be performed first.
Example: To read from block 10, first authenticate using a key from sector 3 (blocks 8-11).
All keys are set to FFFFFFFFFFFFh at chip delivery.
Warning: Please read section 8.7 "Memory Access". It includes this text: if the PICC detects a format violation the whole sector is irreversibly blocked.
 To use a block in "value block" mode (for Increment/Decrement operations) you need to change the sector trailer. Use PICC_SetAccessBits() to calculate the bit patterns.

MIFARE Classic 4K (MF1S703x):

Has (32 sectors4 blocks/sector + 8 sectors16 blocks/sector)16 bytes/block = 4096 bytes.

The blocks are numbered 0-255.
The last block in each sector is the Sector Trailer like above.

MIFARE Classic Mini (MF1 IC S20):

Has 5 sectors4 blocks/sector16 bytes/block = 320 bytes.

The blocks are numbered 0-19.
The last block in each sector is the Sector Trailer like above.

MIFARE Ultralight (MF0ICU1):

Has 16 pages of 4 bytes = 64 bytes.

Pages 0 + 1 is used for the 7-byte UID.
Page 2 contains the last check digit for the UID, one byte manufacturer internal data, and the lock bytes (see https://www.nxp.com/documents/data_sheet/MF0ICU1.pdf section 8.5.2)
Page 3 is OTP, One Time Programmable bits. Once set to 1 they cannot revert to 0.
Pages 4-15 are read/write unless blocked by the lock bytes in page 2. 

MIFARE Ultralight C (MF0ICU2):

Has 48 pages of 4 bytes = 192 bytes.

Pages 0 + 1 is used for the 7-byte UID.
Page 2 contains the last check digit for the UID, one byte manufacturer internal data, and the lock bytes (see https://www.nxp.com/documents/data_sheet/MF0ICU1.pdf section 8.5.2)
Page 3 is OTP, One Time Programmable bits. Once set to 1 they cannot revert to 0.
Pages 4-39 are read/write unless blocked by the lock bytes in page 2. 
Page 40 Lock bytes
Page 41 16 bit one way counter
Pages 42-43 Authentication configuration
Pages 44-47 Authentication key