Datasheet

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CONFIGURATION REGISTER
READING FROM THE ADS1000
WRITING TO THE ADS1000
ADS1000
SBAS357A – SEPTEMBER 2006 – REVISED OCTOBER 2007
A user controls the ADS1000 operating mode and
Bits 1 - 0: PGA
PGA settings via the 8-bit configuration register. The
Bits 1 and 0 control the ADS1000 gain setting; see
configuration register format is shown in Table 3 . The
Table 4 .
default setting is 80H.
Table 4. PGA Bits
Table 3. CONFIGURATION REGISTER
7 6 5 4 3 2 1 0
PGA1 PGA0 GAIN
0
(1)
0
(1)
1
(1)
ST/BSY 0 0 SC 0 0 PGA1 PGA0
0 1 2
Bit 7: ST/BSY
1 0 4
1 1 8
The meaning of the ST/BSY bit depends on whether
(1) Default setting.
it is being written to or read from.
In single conversion mode, writing a '1' to the ST/BSY
bit causes a conversion to start, and writing a '0' has
no effect. In continuous conversion mode, the
ADS1000 ignores the value written to ST/BSY.
A user can read the output register and the contents
When read in single conversion mode, ST/BSY
of the configuration register from the ADS1000. To do
indicates whether the A/D converter is busy taking a
this, address the ADS1000 for reading, and read
conversion. If ST/BSY is read as '1', the A/D
three bytes from the device. The first two bytes are
converter is busy, and a conversion is taking place; if
the output register contents; the third byte is the
'0', no conversion is taking place, and the result of the
configuration register contents.
last conversion is available in the output register.
A user does not always have to read three bytes from
In continuous mode, ST/BSY is always read as '1'.
the ADS1000. If only the contents of the output
Bits 6 - 5: Reserved
register are needed, read only two bytes.
Bits 6 and 5 must be set to zero.
Reading more than three bytes from the ADS1000
has no effect. All of the bytes beginning with the
Bit 4: SC
fourth byte will be FFh. See Figure 7 for a timing
SC controls whether the ADS1000 is in continuous
diagram of an ADS1000 read operation.
conversion or single conversion mode. When SC is
'1', the ADS1000 is in single conversion mode; when
SC is '0', the ADS1000 is in continuous conversion
A user can write new contents into the configuration
mode. The default setting is '0'.
register (the contents of the output register cannot
Bits 3 - 2: Reserved
change). To do this, address the ADS1000 for writing,
and write one byte to it. This byte is written into the
Bits 3 and 2 must be set to zero.
configuration register.
Writing more than one byte to the ADS1000 has no
effect. The ADS1000 ignores any bytes sent to it after
the first one, and will only acknowledge the first byte.
See Figure 8 for a timing diagram of an ADS1000
write operation.
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