Basic Operation
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SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
Analog To Digital Converter (ADC) Module
22.2.2.7 Conversion Result Size on Reading: 8-bit, 10-bit, or 12-bit
Some applications do not need the full 12-bit resolution of the ADC modules on the device and can work
with 8-bit or 10-bit conversion results.
22.2.2.7.1 ADC Configured in 12-bit Resolution
The mode control register for each conversion group contains a field called DATA_FMT, which defines the
format of the conversion result read out of the result RAM, when accessed as a FIFO.
The DATA_FMT field is encoded as follows:
•
If DATA_FMT = 0, the complete 12-bit conversion result is read out of the FIFO.
•
If DATA_FMT = 1h, the 12-bit conversion result is right-shifted by 2 and the resulting 10-bit result is
read out of the FIFO.
•
If DATA_FMT = 2h, the 12-bit conversion result is right-shifted by 4 and the resulting 8-bit result is read
out of the FIFO.
This control field is not effective when the application chooses to access the conversion result memory
directly. In that case, the application can choose to mask off the number of bits as required.
22.2.2.7.2 ADC Configured in 10-bit Resolution
The DATA_FMT field is not effective in this mode and the application has the choice to read either the full
10-bit conversion result or an 8-bit conversion result. This is controlled by the 8BIT field of the group’s
operating mode control register.
•
If 8BIT = 0, the complete 10-bit conversion result is read out of the FIFO.
•
If 8BIT = 1, the 10-bit conversion result is right-shifted by 2 and the resulting 8-bit result is read out of
the FIFO.
22.2.2.8 Option to Read Group Channel ID Along With Conversion Result
The ADC module allows the application program to also read out the analog input channel number along
with its conversion result. This capability is enabled by setting the CHID bit in the group’s operating mode
control register.
•
If CHID = 0, bits [14-10] are forced to 00000 when the conversion results are read out from the group’s
results’ FIFO.
•
If CHID = 1, bits [14-10] in the group’s results’ memory contain the input channel number to which the
conversion result belongs.
NOTE:
Actual Storage of Channel ID
Regardless of whether the CHID bit is set or not, the channel number is
always stored
in
the memory along with the conversion result. The CHID bit only affects whether the channel
number is available with the conversion result
when the group’s memory is read
.
Therefore, the CHID bit for a group can be changed dynamically without affecting that
group’s ongoing conversions.
