mfrc522 NXP Semiconductors, mfrc522 Datasheet - Page 53

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

NXP Semiconductors
112132
Product data sheet
10.4.2 Data validity
10.4.3 START and STOP conditions
Data on the SDA line shall be stable during the HIGH period of the clock. The HIGH or
LOW state of the data line shall only change when the clock signal on SCL is LOW.
To handle the data transfer on the I
are defined.
A START condition is defined with a HIGH to LOW transition on the SDA line while SCL is
HIGH.
A STOP condition is defined with a LOW to HIGH transition on the SDA line while SCL is
HIGH.
The master always generates the START and STOP conditions. The bus is considered to
be busy after the START condition. The bus is considered to be free again a certain time
after the STOP condition.
The bus stays busy if a repeated START (Sr) is generated instead of a STOP condition. In
this respect, the START (S) and repeated START (Sr) conditions are functionally identical.
Therefore, the S symbol will be used as a generic term to represent both the START and
repeated START (Sr) conditions.
Fig 12. Bit transfer on the I
Fig 13. START and STOP conditions.
Rev. 3.2 — 22 May 2007
2
C-bus.
2
C-bus, unique START (S) and STOP (P) conditions
Contactless Reader IC
MFRC522
© NXP B.V. 2007. All rights reserved.
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