READING IN HS MODE
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.
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.
F/S Mode
S
0
0
0
0
1
X
X
X
N
HS Mode Master Code
HS Mode Enabled
ADC Power-Down Mode
ADC Sampling Mode
Sr
1
0
0
1
0
A
A
W
A
SD
C
C
C
PD PD X
0
X
A
1
0
2
1
0
1
Write-Addressing Byte
Command Byte
HS Mode Enabled
ADC Converting Mode
SCLH(2) is stretched LOW waiting for data conversion
Sr
1
0
0
1
0
A
A
R
A
1
0
Read-Addressing Byte
Return to F/S Mode(1)
HS Mode Enabled
ADC Power-Down Mode
(depending on power-down selection bits)
0
0
0
0
D
D
D
D
A
D
D
.D
D
0
N
P
11 10
9
8
7
6 . .
1
2 x (8 Bits + ack/not-ack)
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 Master to Slave
From Slave to Master
NOTES: (1) To remain in HS mode, use repeated START instead of STOP.
(2) SCLH is SCL in HS mode.
FIGURE 4. Typical Read Sequence in HS Mode.
ADS7828
SBAS181C
13
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