Multiple peripherals may request the same shared system bus (BUSAX, BUSAY, BUSBX, etc.). When this happens, a conflict status is
generated and that bus is kept floating. If this happens with the ADC, the PROGERR field in ADCn_STATUS is set to BUSCONF, and
an interrupt may be generated (if enabled). When connecting dedicated I/Os through APORT0, all inputs are available to APORT0X
and APORT0Y and no bus conflict is possible. Refer to
for more information on identifying and resolving bus
conflicts.
Note:
The internal inputs can only be sampled in single channel, single-ended mode. NEGSEL should be fixed to VSS for these con-
versions.
22.3.5.1 Configuring ADC Inputs in Single Channel Mode
In single channel mode, the ADCn_SINGLECTRL register provides the POSSEL and NEGSEL selection for positive and negative
channel selection of the ADC. The APORT Client Map provides external pin to internal bus channel mapping enumeration for a particu-
lar device. Software can also choose internal nodes for POSSEL.
For all single-ended conversions, VSS must be selected in NEGSEL.
Note that in both the POSSEL and NEGSEL fields, it is possible to choose inputs from both X and Y buses, even though X channels
are physically connected to the positive mux (INP_MUX) and Y channels are physically connected to the negative mux (INN_MUX). For
single-ended operation (DIFF = 0), if the positive input is chosen from a Y channel the ADC performs a negative single ended conver-
sion and automatically inverts the result at the end, producing a positive result. For differential conversions (DIFF = 1), if a Y channel is
chosen for the positive input and an X channel is chosen for the negative input, the ADC result will be inverted to produce the correct
polarity.
Refer to
Table 22.1 ADC0 Bus and Pin Mapping on page 725
for specific pin connection options. Note that the same I/O pin may ap-
pear in multiple locations. Enumerations for the POSSEL and NEGSEL fields can be determmined by finding the desired pin connection
in the table and then combining the ADC Port, polarity and channel identifier. For example, pin PF7 is listed as CH23 on APORT2,
polarity X. The enumeration would be APORT2XCH23. PF7 is also available on CH23 of APORT1, polarity Y, so APORT1YCH23 also
selects PF7.
EFM32JG1 Reference Manual
ADC - Analog to Digital Converter
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