LM3S9B81_15 Datasheet, PDF (607/1271 Pages) Texas Instruments – Stellaris LM3S9B81 Microcontroller

Stellaris^® LM3S9B81 Microcontroller
Hysteresis-Once Mode
The Hysteresis-Once operational mode can only be used in conjunction with the low-band or
high-band regions because the mid-band region must be crossed and the opposite region entered
to clear the hysteresis condition. In the Hysteresis-Once mode, the associated interrupt or trigger
is asserted only when the ADC conversion value meets its comparison criteria, the hysteresis
condition is clear, and the previous ADC conversion did not meet the comparison criteria. The result
is a single assertion on the interrupt or trigger.
12.3.7.3
Function Ranges
The two comparison values, COMP0 and COMP1, in the ADC Digital Comparator Range
(ADCDCCMPn) register effectively break the conversion area into three distinct regions. These
regions are referred to as the low-band (less than or equal to COMP0), mid-band (greater than COMP0
but less than or equal to COMP1), and high-band (greater than COMP1) regions. COMP0 and COMP1
may be programmed to the same value, effectively creating two regions, but COMP1 must always
be greater than or equal to the value of COMP0. A COMP1 value that is less than COMP0 generates
unpredictable results.
Low-Band Operation
To operate in the low-band region, either the CIC field field in the ADCDCCTLn register must be
programmed to 0x0. This setting causes interrupts or triggers to be generated in the low-band region
as defined by the programmed operational mode. An example of the state of the interrupt/trigger
signal in the low-band region for each of the operational modes is shown in Figure 12-14 on page 607.
Note that a "0" in a column following the operational mode name (Always, Once, Hysteresis Always,
and Hysteresis Once) indicates that the interrupt or trigger signal is de-asserted and a "1" indicates
that the signal is asserted.
Figure 12-14. Low-Band Operation (CIC=0x0)
COMP1
COMP0
Always – 0 0 0 0 1 1 1 0 0 1 1 0 0 0 0 1
Once – 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 1
Hysteresis Always – 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 1
Hysteresis Once – 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1
July 03, 2014
607
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