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AS7221

I²C Master Interface

Datasheet

• PUBLIC

DS000479

• v4-00 • 2019-Jun-28

│ 25

Random Read and Sequential Read are combined formats. The repeated START condition is used to

change the direction after the data transfer from the master.

The word address transfer is initiated with a START condition issued by the master while the bus is

idle. The START condition is followed by the device-write address and the word address.

In order to change the data direction a repeated START condition is issued on the 1st SCL pulse after

the acknowledge bit of the word address transfer. After the reception of the device-read address, the

slave becomes the transmitter. In this state the slave transmits register data located by the previous

received word address vector. The master responds to the data byte with a not-acknowledge, and

issues a STOP condition on the bus.

Figure 23:

2C Sequential Read(1)

(1)

Shows the format of an I²C sequential read access.

Sequential Read is the extended form of Random Read, as more than one register-data bytes are

transferred subsequently. In difference to the Random Read, for a sequential read the transferred

transferred in one sequence is unlimited (consider the behavior of the word-address counter). To

terminate the transmission the master has to send a not-acknowledge following the last data byte and

generate the STOP condition subsequently.

The AS7221 is compatible to the NXP two wire specifications.

http://www.nxp.com/documents/user_manual/UM10204.pdf Version 4.0 Feb 2012 for standard mode

and fast mode

AS7221 Datasheet(PDF) 26 Page - ams-OSRAM AG