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CLRC663 Datasheet(PDF) 25 Page - NXP Semiconductors |
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CLRC663 Datasheet(HTML) 25 Page - NXP Semiconductors |
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CLRC663 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2012. All rights reserved. Product data sheet COMPANY PUBLIC Rev. 3.3 — 3 April 2012 171133 25 of 132 NXP Semiconductors CLRC663 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 18 “START and STOP conditions”. The number of transmitted bytes during one data transfer is unrestricted but shall fulfil the read/write cycle format. Fig 17. Bit transfer on the I2C-bus. 001aam300 data line stable; data valid change of data allowed SDA SCL Fig 18. START and STOP conditions 001aam301 START condition S SCL SDA SCL SDA STOP condition P |
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