MFRC522 datasheet(68/96 Pages) NXP

68 / 96 page

MFRC522_33

Product data sheet

PUBLIC

Rev. 3 — 26 October 2009

112133

68 of 96

NXP Semiconductors

MFRC522

Contactless reader IC

10.3.1 MFRC522 command descriptions

10.3.1.1

Idle

Places the MFRC522 in Idle mode. The Idle command also terminates itself.

10.3.1.2

Mem

Transfers 25 bytes from the FIFO buffer to the internal buffer.

To read out the 25 bytes from the internal buffer the Mem command must be started with

an empty FIFO buffer. In this case, the 25 bytes are transferred from the internal buffer to

the FIFO.

During a hard power-down (using pin NRSTPD), the 25 bytes in the internal buffer remain

unchanged and are only lost if the power supply is removed from the MFRC522.

This command automatically terminates when ﬁnished and the Idle command becomes

active.

10.3.1.3

Generate RandomID

This command generates a 10-byte random number which is initially stored in the internal

buffer. This then overwrites the 10 bytes in the internal 25-byte buffer. This command

automatically terminates when ﬁnished and the MFRC522 returns to Idle mode.

10.3.1.4

CalcCRC

The FIFO buffer content is transferred to the CRC coprocessor and the CRC calculation is

started. The calculation result 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 buffer is empty during the data stream. The next byte written to the FIFO

buffer is added to the calculation.

The CRC preset value is controlled by the ModeReg register’s CRCPreset[1:0] bits. The

value is loaded in to the CRC coprocessor when the command starts.

This command must be terminated by writing a command to the CommandReg register,

such as, the Idle command.

If the AutoTestReg register’s SelfTest[3:0] bits are set correctly, the MFRC522 enters Self

Test mode. Starting the CalcCRC command initiates a digital self test. The result of the

self test is written to the FIFO buffer.

10.3.1.5

Transmit

The FIFO buffer content is immediately transmitted after starting this command. Before

transmitting the FIFO buffer content, all relevant registers must be set for data

transmission.

This command automatically terminates when the FIFO buffer is empty. It can be

terminated by another command written to the CommandReg register.

10.3.1.6

NoCmdChange

This command does not inﬂuence any running command in the CommandReg register. It

can be used to manipulate any bit except the CommandReg register Command[3:0] bits,

for example, the RcvOff bit or the PowerDown bit.

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