ADS7828 datasheet(13/22 Pages) TI

13 / 22 page

ADS7828

SBAS181C

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FIGURE 4. Typical Read Sequence in HS Mode.

READING IN HS MODE

High Speed (HS) mode is fast enough that codes can be

read out one at a time. In HS mode, there is not enough time

for a single conversion to complete between the reception of

a repeated START condition and the read-addressing byte,

so the ADS7828 stretches the clock after the read-address-

ing byte has been fully received, holding it LOW until the

conversion is complete.

See Figure 4 for a typical read sequence for HS mode.

Included in the read sequence is the shift from F/S to HS

modes. It may be desirable to remain in HS mode after

reading a conversion; to do this, issue a repeated START

instead of a STOP at the end of the read sequence, since a

STOP causes the part to return to F/S mode.

010

001

010

ASD

C2 C1 C0 PD1 PD0 XXA

000

D11 D10 D9 D8

AD7 D6 . . .D1 D0

F/S Mode

HS Mode Master Code

HS Mode Enabled

ADC Power-Down Mode

ADC Sampling Mode

ADC Converting Mode

Command Byte

Write-Addressing Byte

Read-Addressing Byte

HS Mode Enabled

Return to F/S Mode(1)

ADC Power-Down Mode

(depending on power-down selection bits)

2 x (8 Bits + ack/not-ack)

From Master to Slave

A = acknowledge (SDA LOW)

N = not acknowledge (SDA HIGH)

S = START Condition

P = STOP Condition

Sr = repeated START condition

W = '0' (WRITE)

R = '1' (READ)

From Slave to Master

NOTES: (1) To remain in HS mode, use repeated START instead of STOP.

(2) SCLH is SCL in HS mode.

SCLH(2) is stretched LOW waiting for data conversion

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