´
<
-
V
REF
2PGA
2
30
2
1
-
30
DRDY
Data Updating
4/f
CLK
-
V
REF
2PGA
2
30
2
1
-
30
´
-
V
REF
2PGA
(2
1)
´
-
30
V
REF
2PGA
(2
1)
´
-
30
V
REF
2 x PGA
SCLK
DRDY
DOUT
Bit 31
Bit 30
Bit 29
V
REF
2 x PGA
>
SBAS418I – SEPTEMBER 2007 – REVISED MARCH 2015
Serial Interface (continued)
9.25 Data Format
The ADS1282 provides 32 bits of conversion data in
9.24.4 Data Ready (DRDY)
binary
twos
complement
format,
as
shown
in
DRDY is an output; when it transitions low, this
. The LSB of the data is a redundant sign bit:
transition indicates new conversion data are ready, as
'0' for positive numbers and '1' for negative numbers.
shown in
. When reading data by the
However, when the output is clipped to +FS, the
continuous mode, the data must be read within four
LSB = 1; when the output is clipped to –FS, the
CLK periods before DRDY goes low again or the data
LSB = 0. If desired, the data readback may be
are overwritten with new conversion data. When
stopped at 24 bits. Note that in sinc filter mode, the
reading data by the command mode, the read
output data are scaled by 1/2.
operation can overlap the occurrence of the next
DRDY without data corruption.
Table 13. Ideal Output Code Versus Input Signal
INPUT SIGNAL V
IN
32-BIT IDEAL OUTPUT
(AINP – AINN)
CODE
SINC
FIR FILTER
FILTER
7FFFFFFFh
7FFFFFFEh
3FFFFFFFh
Figure 54. DRDY with Data Retrieval
00000002h
00000001h
DRDY resets high on the first falling edge of SCLK.
and
show the function of DRDY
0
00000000h
00000000h
with and without data readback, respectively.
If data are not retrieved (no SCLK provided), DRDY
FFFFFFFFh
FFFFFFFFh
pulses high for four f
CLK
periods during the update
time, as shown in
80000001h
C0000000h
80000000h
(1) Excludes effects of noise, linearity, offset, and gain errors.
Figure 55. DRDY with No Data Retrieval
(2) Due to the reduction in oversampling ratio (OSR) related to
the sinc filter high data rates, full resolution may not be
available.
(3) In sinc filter mode, the output does not clip at half-scale code
when the full-scale range is exceeded.
26
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