AC244027 Microchip Technology, AC244027 Datasheet - Page 131

• Manufacturer Part Number: AC244027
• Description: Processor Extension Pak (PIC16LF727-ICE) 200K Device Emulator - Debugger Accesso
• Manufacturer: Microchip Technology
• Series: -r

Specifications of AC244027

• Accessory Type: Debug Interface Module
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: PIC16F727

14.5
The software portion of the capacitive sensing module
is required to determine the change in frequency of the
capacitive sensing oscillator. This is accomplished by
the following:
• Setting a fixed time base to acquire counts on
• Establishing the nominal frequency for the
• Establishing the reduced frequency for the
• Set the frequency threshold
14.5.1
To determine the nominal frequency of the capacitive
sensing oscillator:
• Remove any extra capacitive load on the selected
• At the start of the fixed time base, clear the timer
• At the end of the fixed time base save the value in
The value of the timer resource is the number of
oscillations of the capacitive sensing oscillator for the
given time base. The frequency of the capacitive
sensing oscillator is equal to the number of counts on
in the timer divided by the period of the fixed time base.
14.5.2
The extra capacitive load will cause the frequency of the
capacitive sensing oscillator to decrease. To determine
the reduced frequency of the capacitive sensing
oscillator:
• Add a typical capacitive load on the selected
• Use the same fixed time base as the nominal
• At the start of the fixed time base, clear the timer
• At the end of the fixed time base save the value in
The value of the timer resource is the number of oscil-
lations of the capacitive sensing oscillator with an addi-
tional capacitive load. The frequency of the capacitive
sensing oscillator is equal to the number of counts on
in the timer divided by the period of the fixed time base.
This frequency should be less than the value obtained
during the nominal frequency measurement.
© 2009 Microchip Technology Inc.
Timer0 or Timer1
capacitive sensing oscillator
capacitive sensing oscillator due to an additional
capacitive load
CPSx pin
resource
the timer resource
CPSx pin
frequency measurement
resource
the timer resource
Software Control
NOMINAL FREQUENCY
(NO CAPACITIVE LOAD)
REDUCED FREQUENCY
(ADDITIONAL CAPACITIVE LOAD)
PIC16F72X/PIC16LF72X
14.5.3
The frequency threshold should be placed midway
between the value of nominal frequency and the
reduced frequency of the capacitive sensing oscillator.
Refer to Application Note AN1103, “Software Handling
for Capacitive Sensing” (DS01103) for more detailed
information the software required for capacitive
sensing module.
Note:
• AN1101, “Introduction to Capacitive
• AN1102, “Layout and Physical Design
FREQUENCY THRESHOLD
For more information on general Capacitive
Sensing refer to Application Notes:
Sensing” (DS01101)
Guidelines for Capacitive Sensing”
(DS01102)
41341E-page 131