mfrc522 NXP Semiconductors, mfrc522 Datasheet - Page 57

• Manufacturer Part Number: mfrc522
• Description: Contactless Reader Ic
• Manufacturer: NXP Semiconductors

NXP Semiconductors
112132
Product data sheet
Fig 17. Register Read and Write Access
SA
SA
10.4.8 Register Read Access
SA
SO
ACK
Nack
(W)
(R)
Optional, if the previous access was on the same register address
SA
I2C slave address
To read out data from a specific register address of the MFRC522 the host controller shall
use the procedure:
First a write access to the specific register address has to be performed as indicated in the
following frame.
The first byte of a frame indicates the device address according to the I
second byte indicates the register address. No data bytes are added.
The read/write bit shall be 0.
Having performed this write access, the read access can start. The host has to send the
device address of the MFRC522. As an answer to this the MFRC522 responds with the
content of this register. In one frame all n-data bytes could be read from the same register
address. This enables for example a fast FIFO access or register polling.
The read/write bit shall be set to logic 1.
I2C slave address
A7-A0
A7-A0
sent by master
sent by slave
start condition
stop condition
acknowledge
not acknowlege
write cycle
read cycle
I2C slave address
A7-A0
(W)
0
(W)
0
Ack
Ack
Rev. 3.2 — 22 May 2007
(R)
1
Write Cycle
0
Ack
0
Read Cycle
0
0
[0..n]
address A5-A0
Joiner register
DATA
[7..0]
address A5-A0
Joiner register
DATA
[7..0]
0..n
Nack
Ack
Ack
Ack
[0..n]
SO
Contactless Reader IC
SO
DATA
[7..0]
SO
MFRC522
© NXP B.V. 2007. All rights reserved.
2
C rules. The
Ack
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