MFRC63002R datasheet(19/118 Pages) NXP

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MFRC630

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Product data sheet

COMPANY PUBLIC

Rev. 3.1 — 6 September 2012

227531

19 of 118

NXP Semiconductors

MFRC630

Contactless reader IC

8.4.4.3

I2C START and STOP conditions

To handle the data transfer on the I2C-bus, unique START (S) and STOP (P) conditions

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.

8.4.4.4

I2C byte format

Each byte has to be followed by an acknowledge bit. Data is transferred with the MSB

first, see Figure 13 “START and STOP conditions”. The number of transmitted bytes

during one data transfer is unrestricted but shall fulfil the read/write cycle format.

Fig 12. Bit transfer on the I2C-bus.

001aam300

data line stable;

data valid

change

of data

allowed

SDA

SCL

Fig 13. START and STOP conditions

001aam301

START condition

SCL

SDA

SCL

SDA

STOP condition

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