ADS7828

13

SBAS181C

www.ti.com

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.

Sr

A1

10

010

A0

RA

SX

00

001

X

X

N

Sr

A1

10

010

A0

W

ASD

C2 C1 C0 PD1 PD0 XXA

000

0

D11 D10 D9 D8

AD7 D6 . . .D1 D0

NP

F/S Mode

HS Mode Master Code

HS Mode Enabled

HS Mode Enabled

ADC Power-Down Mode

ADC Sampling Mode

ADC Converting Mode

Command Byte

Write-Addressing Byte

Read-Addressing Byte

HS Mode Enabled

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.