AD5934
Rev. A | Page 28 of 40
P
READ OPERATIONS
The AD5934 uses two I
2
C 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 35):
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.
S
R
A
A
SLAVE
ADDRESS
REGISTER
DATA
053
25
-0
52
Figure 35. Reading Register Data
Block Read
In this operation, the master device reads a block of data from a
slave device (see Figure 36). 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
W
A
BLOCK
READ
A
A
S
SLAVE
ADDRESS
R
A
BYTE 0
A
BYTE 1
A
BYTE 2
A
P
053
25-
05
3
Figure 36. Performing a Block Read
Содержание AD5934
Страница 35: ...AD5934 Rev A Page 35 of 40 SCHEMATICS 05325 144 Figure 40 EVAL AD5934EBZ USB Schematic ...
Страница 36: ...AD5934 Rev A Page 36 of 40 05325 145 Figure 41 EVAL AD5934EBZ Schematic ...
Страница 37: ...AD5934 Rev A Page 37 of 40 05325 146 Figure 42 Linear Regulator on EVAL AD5934EBZ ...
Страница 38: ...AD5934 Rev A Page 38 of 40 05325 147 Figure 43 Decoupling on the EVAL AD5934EBZ ...