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AD5934 Datasheet(PDF) 26 Page - Analog Devices |
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AD5934 Datasheet(HTML) 26 Page - Analog Devices |
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26 / 31 page 
AD5934 Data Sheet Rev. E | Page 26 of 31 READ OPERATIONS The AD5934 uses two I2C read protocols: the receive byte and the block read. Receive Byte In the AD5934, the receive byte protocol is used to read a single byte of data from a register address whose address has previously been set by setting the address pointer. In this operation, the master device receives a single byte from a slave device as follows (see Figure 29): 1. The master device asserts a start condition on SDA. 2. The master sends the 7-bit slave address followed by the read bit (high). 3. The addressed slave device asserts an acknowledge on SDA. 4. The master receives a data byte. 5. The master asserts a no acknowledge on SDA (the slave needs to check that master has received data). 6. The master asserts a stop condition on SDA and the transaction ends. SR A A P SLAVE ADDRESS REGISTER DATA Figure 29. Reading Register Data Block Read In this operation, the master device reads a block of data from a slave device (see Figure 30). The start address for a block read must previously have been set by setting the address pointer. 1. The master device asserts a start condition on SDA. 2. The master sends the 7-bit slave address followed by the write bit (low). 3. The addressed slave device asserts an acknowledge on SDA. 4. The master sends a command code (1010 0001) that tells the slave device to expect a block read. 5. The slave asserts an acknowledge on SDA. 6. The master sends a byte-count data byte that tells the slave how many data bytes to expect. 7. The slave asserts an acknowledge on SDA. 8. The master asserts a repeat start condition on SDA. This is required to set the read bit high. 9. The master sends the 7-bit slave address followed by the read bit (high). 10. The slave asserts an acknowledge on SDA. 11. The master receives the data bytes. 12. The master asserts an acknowledge on SDA after each data byte. 13. A no acknowledge is generated after the last byte to signal the end of the read. 14. The master asserts a stop condition on SDA to end the transaction. NUMBER BYTES READ S SLAVE ADDRESS WA BLOCK READ AA S SLAVE ADDRESS R A BYTE 0 A BYTE 1 A BYTE 2 A P Figure 30. Performing a Block Read |
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