INTEDG datasheet(330/478 Pages) MICROCHIP

330 / 478 page

PIC16(L)F1946/47

DS41414D-page 330

 2010-2012 Microchip Technology Inc.

26.2.2

CURRENT RANGES

The capacitive sensing oscillator can operate in one of

seven different power modes. The power modes are

separated into two ranges; the low range and the high

range.

When the oscillator’s low range is selected, the fixed

internal voltage references of the capacitive sensing

oscillator are being used. When the oscillator’s high

range is selected, the variable voltage references

supplied by the FVR and DAC modules are being used.

Selection between the voltage references is controlled

by the CPSRM bit of the CPSCON0 register. See

Section 26.2.1 “Voltage Reference Modes”

for more

information.

Within each range there are three distinct Power modes;

low, medium and high. Current consumption is dependent

upon the range and mode selected. Selecting Power

modes within each range is accomplished by configuring

the CPSRNG <1:0> bits in the CPSCON0 register. See

Table 26-1 for proper Power mode selection.

The remaining mode is a Noise Detection mode that

resides within the high range. The Noise Detection

mode is unique in that it disables the sinking and sourc-

ing of current on the analog pin but leaves the rest of

the oscillator circuitry active. This reduces the oscilla-

tion frequency on the analog pin to zero and also

greatly reduces the current consumed by the oscillator

module.

When noise is introduced onto the pin, the oscillator is

driven at the frequency determined by the noise. This

produces a detectable signal at the comparator output,

indicating the presence of activity on the pin.

Figure 26-2 shows a more detailed drawing of the

current sources and comparators associated with the

oscillator.

TABLE 26-1:

POWER MODE SELECTION

26.2.3

TIMER RESOURCES

To measure the change in frequency of the capacitive

sensing oscillator, a fixed time base is required. For the

period of the fixed time base, the capacitive sensing

oscillator is used to clock either Timer0 or Timer1. The

frequency of the capacitive sensing oscillator is equal

to the number of counts in the timer divided by the

period of the fixed time base.

26.2.4

FIXED TIME BASE

To measure the frequency of the capacitive sensing

oscillator, a fixed time base is required. Any timer

resource or software loop can be used to establish the

fixed time base. It is up to the end user to determine the

method in which the fixed time base is generated.

26.2.4.1

Timer0

To select Timer0 as the timer resource for the CPS

module:

• Set the T0XCS bit of the CPSCON0 register.

• Clear the TMR0CS bit of the OPTION_REG

When Timer0 is chosen as the timer resource, the

capacitive sensing oscillator will be the clock source for

Timer0. Refer to Section 20.0 “Timer0 Module” for

additional information.

CPSRM

Range

CPSRNG<1:0>

Current Range

Nominal Current(1)

High

Noise Detection

0.0

A

Low

A

Medium

A

High

100

A

Low

Off

0.0

A

Low

0.25

A

Medium

1.5

A

High

7.5

A

Note 1:

See Section 30.0 “Electrical Specifications” for more information.

Note:

The fixed time base can not be generated

by the timer resource that the capacitive

sensing oscillator is clocking.

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