MFRC522 datasheet(67/96 Pages) NXP

67 / 96 page

MFRC522_33

Product data sheet

PUBLIC

Rev. 3 — 26 October 2009

112133

67 of 96

NXP Semiconductors

MFRC522

Contactless reader IC

10. MFRC522 command set

10.1 General description

The MFRC522 operation is determined by a state machine capable of performing a set of

commands. A command is executed by writing a command code (see Table 149) to the

CommandReg register.

Arguments and/or data necessary to process a command are exchanged via the FIFO

buffer.

10.2 General behavior

• Each command that needs a data bit stream (or data byte stream) as an input

immediately processes any data in the FIFO buffer. An exception to this rule is the

Transceive command. Using this command, transmission is started with the

BitFramingReg register’s StartSend bit.

• Each command that needs a certain number of arguments, starts processing only

when it has received the correct number of arguments from the FIFO buffer.

• The FIFO buffer is not automatically cleared when commands start. This makes it

possible to write command arguments and/or the data bytes to the FIFO buffer and

then start the command.

• Each command can be interrupted by the host writing a new command code to the

CommandReg register, for example, the Idle command.

10.3 MFRC522 command overview

Table 149. Command overview

Command

code

Action

Idle

0000

no action, cancels current command execution

Mem

0001

stores 25 bytes into the internal buffer

Generate RandomID

0010

generates a 10-byte random ID number

CalcCRC

0011

activates the CRC coprocessor or performs a self test

Transmit

0100

transmits data from the FIFO buffer

NoCmdChange

0111

no command change, can be used to modify the

CommandReg register bits without affecting the command,

for example, the PowerDown bit

Receive

1000

activates the receiver circuits

Transceive

1100

transmits data from FIFO buffer to antenna and automatically

activates the receiver after transmission

1101

reserved for future use

MFAuthent

1110

performs the MIFARE standard authentication as a reader

SoftReset

1111

resets the MFRC522

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