mfrc522 NXP Semiconductors, mfrc522 Datasheet - Page 73

• Manufacturer Part Number: mfrc522
• Description: Contactless Reader Ic
• Manufacturer: NXP Semiconductors

NXP Semiconductors
112132
Product data sheet
18.3.1.1 Idle Command
18.3.1.2 Mem Command
18.3.1.3 Generate RandomID Command
18.3.1.4 CalcCRC Command
18.3.1.5 Transmit Command
18.3.1.6 NoCmdChange Command
18.3.1 MFRC522 Command Description
The MFRC522 is in Idle mode. This command is also used to terminate the actual
command.
Transfers 25 byte from the FIFO to the internal buffer.
To read out the 25 byte from the internal buffer, the command Mem with an empty FIFO
buffer has to be started. In this case the 25 bytes are transferred from the internal buffer to
the FIFO.
During a hard power down (reset pin) the 25 byte in the internal buffer remains unchanged
but will be lost when supply power is removed from MFRC522.
This command terminates automatically when finished and the active command is idle.
This command generates a 10 byte random number stored in the internal buffer and
overwrites the 10 bytes internal 25 byte buffer. This command terminates automatically
when finished and the MFRC522 returns to idle.
The content of the FIFO is transferred to the CRC co-processor and a CRC calculation is
started. The result of this calculation is stored in the CRCResultReg register. The CRC
calculation is not limited to a dedicated number of bytes. The calculation is not stopped,
when the FIFO gets empty during the data stream. The next byte written to the FIFO is
added to the calculation.
The pre-set value of the CRC is controlled by the CRCPreset bits of the ModeReg register
and the value is loaded to the CRC co-processor when the command is started.
This command has to be terminated by writing any command to register CommandReg
e.g. the command Idle.
If the SelfTest bits in the register AutoTestReg are set correct, the MFRC522 is in Self Test
mode and starting the CalCCRC command performs a digital selftest. The result of the
selftest is written to the FIFO.
The content of the FIFO is transmitted immediately after starting the command. Before
transmitting the FIFO content all relevant register have to be set to transmit data.
This command terminates automatically when the FIFO gets empty. It can be terminated
by any other command written to the command register.
This command does not influence any ongoing command in the CommandReg register. It
can be used to manipulate any bit except the command bits in the CommandReg register,
e.g. the bits RcvOff or PowerDown.
Rev. 3.2 — 22 May 2007
Contactless Reader IC
MFRC522
© NXP B.V. 2007. All rights reserved.
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