All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2010. All rights reserved.
Product data sheet
Rev. 3.4 — 5 March 2010
10 of 96
Contactless reader IC
SPI write data
To write data to the MFRC522 using SPI requires the byte order shown in Table 7. It is
possible to write up to n data bytes by only sending one address byte.
The first send byte defines both the mode and the address byte.
X = Do not care.
Remark: The MSB must be sent first.
SPI address byte
The address byte must meet the following format.
The MSB of the first byte defines the mode used. To read data from the MFRC522 the
MSB is set to logic 1. To write data to the MFRC522 the MSB must be set to logic 0. Bits 6
to 1 define the address and the LSB is set to logic 0.
8.1.3 UART interface
Connection to a host
Remark: Signals DTRQ and MX can be disabled by clearing TestPinEnReg register’s
MOSI and MISO byte order
Byte n + 1
− 1data n
Address byte 0 register; address MOSI
1 = read
0 = write
UART connection to microcontrollers