MFRC522 datasheet(73/109 Pages) NXP

73 / 109 page

112132

Product data sheet

Rev. 3.2 — 22 May 2007

73 of 109

NXP Semiconductors

MFRC522

Contactless Reader IC

18.3.1 MFRC522 Command Description

18.3.1.1

Idle Command

The MFRC522 is in Idle mode. This command is also used to terminate the actual

command.

18.3.1.2

Mem 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.

18.3.1.3

Generate RandomID Command

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.

18.3.1.4

CalcCRC Command

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.

18.3.1.5

Transmit Command

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.

18.3.1.6

NoCmdChange Command

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.

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