National CP3BT26 - Manual (Page 87)

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CP3
BT26
16.5.6 ADC Result Register (ADCRESLT)
The ADCRESLT register includes the software-visible end
of a 4-word FIFO. Conversion results are loaded into the
FIFO from the 12-bit ADC and unloaded when software
reads the ADCRESLT register. The ADCRESLT register is
read-only. With the exception of the PEN_DOWN bit, the
fields in this register are cleared when the register is read.
ADC_RESULT The ADC Result field holds a 12-bit value for
the conversion result. If the ADC_DONE bit is
clear, there is no valid result in this field, and
the field will have a value of 0. The
ADC_RESULT field and the SIGN bit together
form the software-visible end of the ADC
FIFO.
SIGN The Sign bit indicates whether the - input has
a voltage greater than the + input (differential
mode only). For example if AD-
CGCR.MUX_CFG is 000b, ADC0 is the + in-
put and ADC1 is the - input. If the voltage on
ADC0 is greater than the voltage on ADC1,
the SIGN bit will be 0; if the voltage on ADC0
is less than the voltage on ADC1, the SIGN bit
will be 1. In single-ended mode, this bit always
reads as 0.
0 – In differential mode, + input has a voltage
greater than the - input. In single-ended
mode, this bit is always 0.
1 – In differential mode, - input has a voltage
greater than the + input.
PEN_DOWN The Pen-Down bit indicates whether a pen-
down condition is being sensed. To enable
pen-down detection, the TOUCH_CFG field of
the ADCGCR register must be loaded with
101b. When pen-down detection is enabled
and a pen-down condition is sensed, the
PEN_DOWN bit is set. This bit is not carried
through the FIFO, so its value represents the
current status of the pen-down detector.
When pen-down detection is enabled, the sig-
nal from the pen-down detector is ORed with
the Done signal to generate the wake-up sig-
nal (WUI30) passed to the MIWU unit. If pen-
down detection is not enabled, this bit reads
as 0.
0 – No pen-down condition is sensed, or pen-
down detection is disabled.
1 – Pen-down condition is sensed.
ADC_OFLW The ADC FIFO Overflow bit indicates whether
the 4-word FIFO behind the ADCRESLT reg-
ister has overflowed. When this occurs, the
most recent conversion result is lost. This bit
is cleared when the ADCRESLT register is
read.
0 – FIFO overflow has not occurred.
1 – FIFO overflow has occurred.
ADC_DONE The ADC Done bit indicates when an ADC
conversion has completed. When this bit is
set, the data in the ADC_RESULT field is val-
id. When this bit is clear, there is no valid data
in the ADC_RESULT field. The Done bit is
cleared when the ADCRESLT register is read,
but if there are queued conversion results in
the FIFO, the Done bit will become set again
after one System Clock period.
0 – No ADC conversion has completed since
the ADCRESLT register was last read.
1 – An ADC conversion has completed since
the ADCRESLT register was last read.
11 0
ADC_RESULT
15 14 13 12
ADC_DONE ADC_OFLW PEN_DOWN SIGN