© NXP B.V. 2009. All rights reserved.
Product data sheet
Rev. 3 — 26 October 2009
9 of 96
Contactless reader IC
8.1.2 Serial Peripheral Interface
A serial peripheral interface (SPI compatible) is supported to enable high-speed
communication to the host. The interface can handle data speeds up to 10 Mbit/s. When
communicating with a host, the MFRC522 acts as a slave, receiving data from the
external host for register settings, sending and receiving data relevant for RF interface
An interface compatible with SPI enables high-speed serial communication between the
MFRC522 and a microcontroller. The implemented interface is in accordance with the SPI
The timing speciﬁcation is given in Section 14.1 on page 75.
The MFRC522 acts as a slave during SPI communication. The SPI clock signal SCK must
be generated by the master. Data communication from the master to the slave uses the
MOSI line. The MISO line is used to send data from the MFRC522 to the master.
Data bytes on both MOSI and MISO lines are sent with the MSB ﬁrst. Data on both MOSI
and MISO lines must be stable on the rising edge of the clock and can be changed on the
falling edge. Data is provided by the MFRC522 on the falling clock edge and is stable
during the rising clock edge.
SPI read data
Reading data using SPI requires the byte order shown in Table 6 to be used. It is possible
to read out up to n-data bytes.
The ﬁrst byte sent deﬁnes both the mode and the address.
X = Do not care.
Remark: The MSB must be sent ﬁrst.
SPI connection to host
MOSI and MISO byte order
Byte n + 1