ADS7828-Q1
SBAS456A –DECEMBER 2008–REVISED OCTOBER 2009.......................................................................................................................................... www.ti.com
Reading Data
Data can be read from the ADS7828 by read addressing the part (LSB of address byte set to 1) and receiving
the transmitted bytes. Converted data can be read from the ADS7828 only after a conversion has been initiated
as described in the preceding section.
Each 12-bit data word is returned in two bytes (see Figure 6), where D11 is the MSB of the data word, and D0 is
the LSB. Byte 0 is sent first, followed by byte 1.
MSB
0
6
0
5
0
4
0
3
2
1
LSB
D8
Byte 0
Byte 1
D11
D3
D10
D2
D9
D1
D7
D6
D5
D4
D0
Figure 6. Reading Data
Reading in Fast or Standard (F/S) Mode
Figure 7 shows the interaction between the master and the slave ADS7828 in fast or standard (F/S) mode. At the
end of reading conversion data, the ADS7828 can be issued a repeated Start condition by the master to secure
bus operation for subsequent conversions of the A/D converter. This would be the most efficient way to perform
continuous conversions.
ADC Power-Down Mode
ADC Sampling Mode
S
1
0
0
1
0
A1 A0
W
A
SD C2 C1 C0 PD1 PD0
Command Byte
X
X
A
Write-Addressing Byte
ADC Converting Mode
ADC Power-Down Mode
(depending on power-down selection bits)
Sr
1
0
0
1
0
A1 A0
R
A
0
0
0
0
D11 D10 D9 D8
A
D7 D6...D1 D0
N
P
See Note (1)
Read-Addressing Byte
2 x (8 bits + ack/nack)
A = Acknowledge (SDA low)
N = Not acknowledge (SDA high)
S = Start condition
W = 0 (write)
R = 1 (read)
From Master to Slave
From Slave to Master
P = Stop condition
Sr = Repeated Start condition
NOTE: (1) To secure bus operation and loop back to the stage of write-addressing for next conversion, use Repeated Start.
Figure 7. Typical Read Sequence in F/S Mode
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