AD5933 datasheet(29/40 Pages) AD

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Data Sheet

AD5933

Rev. F | Page 29 of 40

READ OPERATIONS

The AD5933 uses two I2C read protocols: receive byte and

block read.

Receive Byte

In the AD5933, 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 33):

The master device asserts a start condition on SDA.

The master sends the 7-bit slave address followed by the

read bit (high).

The addressed slave device asserts an acknowledge on SDA.

The master receives a data byte.

The master asserts a no acknowledge on SDA (the slave

needs to check that master has received data).

The master asserts a stop condition on SDA and the

transaction ends.

SLAVE

ADDRESS

DATA

Figure 33. Reading Register Data

Block Read

In this operation, the master device reads a block of data from a

slave device (see Figure 34). The start address for a block read

must previously have been set by setting the address pointer.

The master device asserts a start condition on SDA.

The master sends the 7-bit slave address followed by the

write bit (low).

The addressed slave device asserts an acknowledge on SDA.

The master sends a command code (1010 0001) that tells

the slave device to expect a block read.

The slave asserts an acknowledge on SDA.

The master sends a byte-count data byte that tells the slave

how many data bytes to expect.

The slave asserts an acknowledge on SDA.

The master asserts a repeat start condition on SDA. This is

required to set the read bit high.

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

SLAVE

ADDRESS

BLOCK

READ

SLAVE

ADDRESS

BYTE 0

BYTE 1

BYTE 2

Figure 34. Performing a Block Read

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