Specifications

Self-Test
7-19 Analog-to-Digital Converter (ADC)
7.5 Self-Test
The self-test mode is a way to detect shorts/opens on an ADC pin. The sam-
pling period is doubled in this mode. In the first half of the sampling period, ei-
ther V
REFHI
or V
REFLO
(as determined by the HI/LO bit) is connected to the in-
put of the A/D converter, in addition to the analog input signal provided by the
user. In the second half of the sampling period, only user signal is connected
to the ADC. Assuming there is an open (and V
REFHI
is used), the result register
would contain the digital representation of V
REFHI
only.
The self-test mode should be used only to check for shorts and opens. It should
not be used during normal operation. In addition, the calibration mode and the
self-test mode should not be enabled at the same time.