MFRC522 datasheet(72/109 Pages) NXP

72 / 109 page

112132

Product data sheet

Rev. 3.2 — 22 May 2007

72 of 109

NXP Semiconductors

MFRC522

Contactless Reader IC

18. MFRC522 Command Set

18.1 General Description

The behavior is determined by a state machine capable to perform a certain set of

commands. By writing the according command-code to register CommandReg the

command is executed.

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

buffer.

18.2 General Behavior

• Each command, that needs a data stream (or data byte stream) as input will

immediately process the data it finds in the FIFO buffer. An exception to this rule is the

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

StartSend bit in the BitFramingReg register.

• Each command that needs a certain number of arguments will start processing only

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

• The FIFO buffer is not cleared automatically at command start. Therefore, it is also

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

and start the command afterwards.

• Each command may be interrupted by the host by writing a new command code into

18.3 MFRC522 Commands Overview

Table 149: Command overview

Command

Command code

Action

Idle

0000

No action; cancels current command execution.

Mem

0001

Stores 25 byte into the internal buffer

Generate

RandomID

0010

Generates a 10 byte random ID number

CalcCRC

0011

Activates the CRC co-processor or performs a selftest.

Transmit

0100

Transmits data from the FIFO buffer.

NoCmd

Change

0111

No command change. This command can be used to modify

different bits in the command register without touching the

command. E.g. Power-down.

Receive

1000

Activates the receiver circuitry.

Transceive

1100

Transmits data from FIFO buffer to the antenna and activates

automatically the receiver after transmission.

1101

Reserved for further use

MFAuthent

1110

Performs the MIFARE® standard authentication as a reader

Soft Reset

1111

Resets the MFRC522

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