ADS7924 Datasheet, PDF (30/42 Pages) Texas Instruments – 2.2V, 12-Bit, 4-Channel, microPOWER™ ANALOG-TO-DIGITAL CONVERTER WITH I2C INTERFACE

ADS7924
SBAS482A – JANUARY 2010 – REVISED MAY 2010
READING THE REGISTERS
To read a specific register from the ADS7924, the
master must first write the appropriate value to the
pointer address. The pointer address is written
directly after the slave address byte, low R/W bit, and
a successful slave acknowledgment. The MSB of the
pointer address is the INC bit. When set to '1', the
register address is automatically incremented after
every register read which allows convenient reading
of multiple registers. Set INC to '0' when reading a
single register.
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The master may issue a START condition and send
the slave address byte with the R/W bit high to begin
the read. Note that if the previously selected register
is to be read again there is no need to update the
pointer address. Figure 32 to Figure 34 show
examples of register reads.
1
SCL
91
9
¼
SDA
1
Start By
Master
0
0
1
0
0 A0⁽¹⁾ R/W
0⁽²⁾ 0
Frame 1 Slave Address Byte
ACK By
ADS7924
0 P4⁽³⁾ P3 P2 P1 P0
ACK By
ADS7924
Frame 2 Pointer Address Byte
Stop By
Master
1
91
9
SCL
(Continued)
SDA
(Continued)
1
Start By
Master
0
0
1
0
0 A0⁽¹⁾ R/W
D7 D6 D5 D4 D3 D2 D1 D0
Frame 3 Slave Address Byte
ACK By
ADS7924
From
ADS7924
Frame 4 Data Byte
ACK By
Master⁽²⁾
(1) The value of A0 is determined by the A0 pin.
(2) When INC is set to '0', the address pointer remains unchanged after a read.
(3) Bits P[4:0] point to the register to be read.
Figure 32. Reading a Single Register Timing Diagram
1
91
9
SCL
SDA
1
Start By
Master
0
0
1
0
0 A0⁽¹⁾ R/W
D7 D6 D5 D4 D3 D2 D1 D0
Frame 1 Slave Address Byte
ACK By
ADS7924
Frame 2 Register Data Byte
ACK By
ADS7924
Stop By
Master
(1) The value of A0 is determined by the A0 pin.
Figure 33. Reading a Previously Addressed Register Timing Diagram
30
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