ADS7828-Q1

SBAS456B – DECEMBER 2008 – REVISED JANUARY 2016

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7.4.2 Command Byte

The operating mode is determined by a command byte (see Figure 16).

Figure 16. Command Byte

MSB

6

5

4

3

2

1

LSB

SD

C2

C1

C0

PD1

PD0

X

X

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

C2

C1

C0

CH0

CH1

CH2

CH3

CH4

CH5

CH6

CH7

COM

0

0

0

0

+IN

–IN

—

—

—

—

—

—

—

0

0

0

1

—

—

+IN

–IN

—

—

—

—

—

0

0

1

0

—

—

—

—

+IN

–IN

—

—

—

0

0

1

1

—

—

—

—

—

—

+IN

–IN

—

0

1

0

0

–IN

+IN

—

—

—

—

—

—

—

0

1

0

1

—

—

–IN

+IN

—

—

—

—

—

0

1

1

0

—

—

—

—

–IN

+IN

—

—

—

0

1

1

1

—

—

—

—

—

—

–IN

+IN

—

1

0

0

0

+IN

—

—

—

—

—

—

—

–IN

1

0

0

1

—

—

+IN

—

—

—

—

—

–IN

1

0

1

0

—

—

—

—

+IN

—

—

—

–IN

1

0

1

1

—

—

—

—

—

—

+IN

—

–IN

1

1

0

0

—

+IN

—

—

—

—

—

—

–IN

1

1

0

1

—

—

—

+IN

—

—

—

—

–IN

1

1

1

0

—

—

—

—

—

+IN

—

—

–IN

1

1

1

1

—

—

—

—

—

—

—

+IN

–IN

Table 2. Power-Down Selection

PD1

PD0

DESCRIPTION

0

0

Power down between ADC conversions

0

1

Internal reference off and ADC on

1

0

Internal reference on and ADC off

1

1

Internal reference on and ADC on

7.4.3 Initiating Conversion

Provided the master has write-addressed it, the ADS7828 turns on the ADC section and begins conversions

when it receives bit 4 of the command byte shown in Figure 16. If the command byte is correct, the ADS7828

returns an ACK condition.

18

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