GX4002 Datasheet, PDF (43/74 Pages) Gennum Corporation – Dynamic on-chip power management control

3.7.1.3.2 OFFSET CORRECTION
The ADC supports offset correction for both internal offsets as well as external
systematic offsets through the ADCOFFSETLO and ADCOFFSETHI registers.
The offset correction behaviour depends on the ADCOFFMODE control bit. Table 3-3
describes the offset correction operation:
Table 3-3: Offset Correction Operation
ADCOFFMODE
0
1
Operation
ADCOUTLO,HI = uncorrected
ADC Out[15:0] -
ADCOFFSETLO,HI
ADCOUTLO,HI = uncorrected
ADC Out[15:0] +
ADCOFFSETLO,HI
Description
ADCOFFSETLO,HI is un-signed.
Result is unsigned. Output is all 0s
for negative results.
ADCOFFSETLO,HI is sign + mag.
Bit 15 is sign, and 1 represents
positive. Result is unsigned. Output
is all 0s for negative results.
Supporting both subtraction and addition of offsets allows the user the flexibility to
adjust for systematic shifts. However, the default mode 0 (subtraction) should suffice for
most applications.
In the previous example, the offset was measured to be 10 for ADCOUT = 521 for the
temperature sensor. This offset can be automatically subtracted for all subsequent
measurements of the temperature sensor by setting ADCOFFSETLO = 10 and
ADCOFFSETHI = 0. With these values, ADCOUT will read 511 (instead of 521).
3.7.1.4 ADC Conversion Sequence
The following sequence is recommended for ADC conversions:
1. Power-up the ADC.
2. Bring the ADC out of reset.
3. Setup the ADC mode of operation (Auto or Manual).
4. Setup the ADC resolution.
5. Setup the ADC conversion rate (clock rate).
6. Select the ADC source to convert.
7. Setup the ADC offset and offset modes.
8. Start the ADC conversion.
9. Read the ADC-done conversion flag to confirm a successful conversion.
10. Read the ADC output, first the low byte, immediately followed by high byte.
The following section gives a detailed example of performing an ADC conversion in
manual mode.
GX4002 2x2 14.025Gb/s Crosspoint Switch with Trace
Equalization and Output De-Emphasis
Data Sheet
55972 - 0
March 2012
43 of 74
Proprietary & Confidential