Datasheet

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 A
1
10010 A
0
RA
SX00001 XXN
Sr A
1
10010 A
0
W ASDC
2
C
1
C
0
PD
1
PD
0
XXA
0000D
11
D
10
D
9
D
8
AD
7
D
6 . .
.D
1
D
0
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 ByteWrite-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