ADS1274
ADS1278
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SBAS367–JUNE 2007
TDM Mode, Fixed-Position Data
Discrete Data Output Mode
In this TDM data output mode, the data position of
the channels remain fixed, regardless of whether the
channels are powered down. If a channel is powered
down, the data are forced to zero but occupy the
same position within the data stream. Figure 78
shows the data stream with channel 1 and channel 3
powered down.
In Discrete data output mode, the channel data are
shifted out in parallel using individual channel data
output pins DOUT[4:1]/[8:1]. After the 24th SCLK, the
channel data are forced to zero. The data are also
forced to zero for powered down channels. Figure 80
shows the discrete data output format.
TDM Mode, Dynamic Position Data
In this TDM data output mode, when a channel is
powered down, the data from higher channels shift
one position in the data stream to fill the vacated data
slot. Figure 79 shows the data stream with channel 1
and channel 3 powered down.
SCLK
1
2
23
24
25
47
48
49
71
72
73
95
96
97
167
168
169
191
192
193
194
195
DOUT1
(ADS1274)
CH1
CH2
CH3
CH4
DIN
CH5
DOUT1
(ADS1278)
CH1
CH2
CH3
CH4
CH7
CH8
DIN
DRDY
(SPI)
FSYNC
(Frame-Sync)
Figure 78. TDM Mode, Fixed-Position Data (Channels 1 and 3 Shown Powered Down)
SCLK
1
2
23
24
25
47
48
49
50
119
120
121
143
144
145
145
146
DOUT1
(ADS1274)
CH2
CH4
DIN
DOUT1
(ADS1278)
CH2
CH4
CH5
CH7
CH8
DIN
DRDY
(SPI)
FSYNC
(Frame- Sync)
Figure 79. TDM Mode, Dynamic Position Data (Channels 1 and 3 Shown Powered Down)
32
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