AD8158 查看數據表（PDF） - Analog Devices
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AD8158 Datasheet PDF : 36 Pages
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AD8158
I2C INTERFACE DATA TRANSFERS: DATA READ
To read data from the AD8158 register set, a microcontroller
or any other I2C master needs to send the appropriate control
signals to the AD8158 slave device. The following steps need
to be taken, where the signals are controlled by the I2C master,
unless otherwise specified. For a diagram of the procedure, see
Figure 44.
1. Send a start condition (while holding the SCL line high,
pull the SDA line low).
2. Send the AD8158 part address (seven bits) whose upper
four bits are the static value b1010 and whose lower three
bits are controlled by the I2C_A[2:0] input pins. This
transfer should be MSB first.
3. Send the write indicator bit (0).
4. Wait for the AD8158 to acknowledge the request.
5. Send the register address (eight bits) from which data is to
be read. This transfer should be MSB first. The register
address is kept in memory in the AD8158 until the part is
reset or the register address is written over with the same
procedure (Step 1 to Step 6).
6. Wait for the AD8158 to acknowledge the request.
7. Send a repeated start condition (while holding the SCL line
high, pull the SDA line low).
8. Send the AD8158 part address (seven bits) whose upper
four bits are the static value b1010 and whose lower three
bits are controlled by the I2C_A[2:0] input pins. This
transfer should be MSB first.
9. Send the read indicator bit (1).
10. Wait for the AD8158 to acknowledge the request.
11. The AD8158 then serially transfers the data (eight bits)
held in the register indicated by the address set in Step 5.
12. Acknowledge the data.
SCL
13a. Send a stop condition (while holding the SCL line high,
pull the SDA line high) and release control of the bus.
13b. Send a repeated start condition (while holding the SCL
line high, pull the SDA line low) and continue with Step 2
of the write procedure (see the I2C Interface Data
Transfers: Data Write section) to perform a write.
13c. Send a repeated start condition (while holding the SCL
line high, pull the SDA line low) and continue with Step 2
of this procedure to perform a read from another address.
13d. Send a repeated start condition (while holding the SCL
line high, pull the SDA line low) and continue with Step 8
of this procedure to perform a read from the same address.
In Figure 44, the AD8158 read process is shown. The SCL signal is
shown along with a general read operation and a specific example.
In this example, the value 0x49 is read from Address 0x6D of
an AD8158 device with a 0x53 part address. The part address
is seven bits wide and is composed of the AD8158 static upper
four bits (b1010) and the pin-programmable lower three bits
(I2C_A[2:0]). The address pins are set to b011. In Figure 44, the
corresponding step number is visible in the circle under the
waveform. The SCL line is driven by the I2C master and never
by the AD8158 slave. As for the SDA line, the data in the shaded
polygons is driven by the AD8158, whereas the data in the
nonshaded polygons is driven by the I2C master. The end phase
case shown is that of Step 13A.
It is important to note that the SDA line only changes when
the SCL line is low, except for the case of sending a start, stop,
or repeated start condition, as in Step 1, Step 7, and Step 13.
In Figure 44, A is the same as ACK. Equally, Sr represents a
repeated start where the SDA line is brought high before SCL
is raised. SDA is then dropped while SCL is still high.
SDA START
b11110
ADDR R/
[1:0] W
A
REGISTER ADDR
A Sr
FIXED PART
ADDR
ADDR
[1:0]
R/
W
A
SDA
1
2
2 34
5
67
8
Figure 44. I2C Read Diagram
8 9 10
DATA
11
A STOP
12 13a
Rev. 0 | Page 30 of 36
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