ADS7828-Q1
www.ti.com.......................................................................................................................................... SBAS456A –DECEMBER 2008–REVISED OCTOBER 2009
Command Byte
The operating mode is determined by a command byte (see Figure 5).
MSB
SD
6
5
4
3
2
1
LSB
X
C2
C1
C0
PD1
PD0
X
Figure 5. Command Byte
SD: Single-ended or differential inputs
0 = Differential inputs
1 = Single-ended inputs
C2 to C0: Channel selections (see Table 1)
PD1, PD0: Power-down selection (see Table 2)
X: Unused
Table 1. Channel Selection Control Addressed by Command Byte
COMMAND BYTE INPUTS
CHANNEL SELECTIONS
SD
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
C2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
C1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
C0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
CH0
+IN
—
CH1
–IN
—
CH2
—
CH3
—
CH4
—
CH5
—
CH6
—
CH7
—
COM
—
—
+IN
—
–IN
—
—
—
—
—
—
—
+IN
—
–IN
—
—
—
—
—
—
—
—
+IN
—
–IN
—
—
–IN
—
+IN
—
—
—
—
—
—
–IN
—
+IN
—
—
—
—
—
—
—
—
–IN
—
+IN
—
—
—
—
—
—
—
—
–IN
—
+IN
—
—
+IN
—
—
—
—
—
—
–IN
–IN
–IN
–IN
–IN
–IN
–IN
–IN
—
+IN
—
—
—
—
—
—
—
—
—
+IN
—
—
—
—
—
—
—
—
—
+IN
—
—
—
+IN
—
—
—
—
—
—
—
—
+IN
—
—
—
—
—
—
—
—
—
+IN
—
—
—
—
—
—
—
—
—
+IN
Table 2. Power-Down Selection
PD1
PD0
DESCRIPTION
Power down between A/D converter conversions
Internal reference off and A/D converter on
Internal reference on and A/D converter off
Internal reference on and A/D converter on
0
0
1
1
0
1
0
1
Initiating Conversion
Provided the master has write-addressed it, the ADS7828 turns on the A/D converter section and begins
conversions when it receives bit 4 of the command byte shown in Figure 5. If the command byte is correct, the
ADS7828 returns an ACK condition.
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