Datasheet

D7 D6 D5 D4 D3 D2 D1 D0
1 9
1 9
Ack by
ADC128D818
Start by
Master
R/W
Frame 1
Serial Bus Address
Byte from Master
Frame 2
Register Address
Byte from Master
A2
A0A1
A3A4A5A6
SCL
SDA
Stop by
Master
Ack by
ADC128D818
ADC128D818
SNAS483E –FEBRUARY 2010–REVISED MARCH 2013 www.ti.com
INTERFACE
The Serial Bus control lines include the SDA (serial data), SCL (serial clock), and A0-A1 (Serial Bus Address)
pins. The ADC128D818 can only operate as a slave. The SCL line only controls the serial interface, and all of
other clock functions within ADC128D818 are done with a separate asynchronous internal clock.
When the Serial Bus Interface is used, a write will always consists of the ADC128D818 Serial Bus Address byte,
followed by the Register Address byte, then the Data byte. Figure 27 and Figure 28 are two examples showing
how to write to the ADC128D818.
There are two cases for a read:
1. If the Register Address is known to be at the desired address, simply read the ADC128D818 with the Serial
Bus Address byte, followed by the Data byte read from the ADC128D818. Examples of this type of read can
be seen in Figure 29 and Figure 30.
2. If the Register Address value is unknown, write to the ADC128D818 with the Serial Bus Address byte,
followed by the desired Register Address byte. Then restart the Serial Communication with a Read
consisting of the Serial Bus Address byte, followed by the Data byte read from the ADC128D818. See
Figure 31 and Figure 32 for examples of this type of read.
The Serial Bus Address can be found in the next section, and the Register Address can be found in the
REGISTER MAP section. For more information on the I
2
C Interface, refer to NXP's "I
2
C-Bus Specification and
User Manual", rev. 03.
Serial Bus Address
There are nine different configurations for the ADC128D818 Serial Bus Address, thus nine devices are allowed
on a single I
2
C bus. Examples to set each address bit low, high, or to midscale can be found in the EXAMPLE
APPLICATIONS section. The Serial Bus Address can be set as follows:
Table 5. Serial Bus Address Table
Serial Bus Address
A1 A0 [A6][A5][A4]...[A0] Serial Bus Address (hex)
LOW LOW 001_1101b 1Dh
LOW MID 001_1110b 1Eh
LOW HIGH 001_1111b 1Fh
MID LOW 010_1101b 2Dh
MID MID 010_1110b 2Eh
MID HIGH 010_1111b 2Fh
HIGH LOW 011_0101b 35h
HIGH MID 011_0110b 36h
HIGH HIGH 011_0111b 37h
Timeout
The ADC128D818 I
2
C state machine resets to its idle state if either SCL or SDA is held low for longer than
35ms. This feature also ensures that ADC128D818 will automatically release SDA after driving it low
continuously for 25-35ms, hence preventing I
2
C bus lock-up. The TIMEOUT feature should not be used when the
device is operating in deep shutdown mode.
Example Writes and Reads
Figure 27. Serial Bus Interface Write Example 1 - Internal Address Register Set Only.
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