DM163035+TEFLCST3 Microchip Technology, DM163035+TEFLCST3 Datasheet - Page 80

• Manufacturer Part Number: DM163035+TEFLCST3
• Description: KIT, PICDEMLAB+FLOWCODE-HOME BUNDLE/
• Manufacturer: Microchip Technology

Specifications of DM163035+TEFLCST3

• Kit Contents: Component Kit, PICDEM Lab Development Board, PICkit 2 Programmer/ Debugger, CD Containing User Guide
• Svhc: No SVHC (15-Dec-2010)
• Development Tool Type: Hardware / Software - Dev
• Silicon Manufacturer: Microchip
• Core Architecture: PIC
• Core Sub-architecture: PIC10, PIC12, PIC16
• Silicon Core Number: PIC10F, PIC12F, PIC16F
• Silicon Family Name: PIC10F2xx, PIC12F6xx, PIC16F6xx
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PICDEM
DS41381A-page 76
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discharge the capacitor to 37% of its initial voltage. As either the resistance or
capacitance decreases, so will τ effectively increasing the frequency of the oscillator. If
the resistor is replaced with a Negative Temperature Coefficient (NTC) thermistor
where resistance decreases as temperature increases, any temperature change would
cause a shift in resistance with a subsequent shift in the frequency of the oscillator.
This oscillator can be created quite easily by simply initializing the comparator and
nothing more. However, with the addition of some intelligence and some additional
peripherals, a higher resolution sensor measurement application can be achieved.
A common feature found on most PIC
peripheral Timer0. This timer can either use the internal instruction clock (F
its time base or an external clock source on the Timer0 Clock Input (T0CKI) pin to
increment the value in an 8-bit result register TMR0. In this application, the oscillator
described will be used as the Timer0 clock source. The Timer0 peripheral will be
configured to increment the TMR0 register value with each low-to-high transition on the
T0CKI pin effectively counting the number of pulses. This peripheral also features an
interrupt on overflow. So, after 256 counts (0-255 inclusive), TMR0 will overflow
triggering an interrupt. A counter variable within the main loop of the application will be
used to count each time through the Software Control loop. On a Timer0 interrupt, the
current value of the counter variable will be assigned to four LEDs connected to the
PORTB RB4, RB5, RB6, RB7 pins. If heat is applied to the thermistor, the effective
resistance will drop and the oscillator frequency will increase. Since the oscillator is the
clock source for the Timer0 peripheral, TMR0 will overflow sooner and the counter
variable value would be less. Colder temperatures will increase the effective
resistance, slow the oscillator frequency and subsequently the overflow interrupt period
and a higher counter value will be obtained. In other words:
increase temp. = increased oscillator frequency = decrease counter value
decrease temp. = decreased oscillator frequency = increased counter value
The schematic for this lab is shown in Figure 3-11.
Lab Flowcode Companion Guide
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microcontrollers is the 8-bit timer/counter
© 2009 Microchip Technology Inc.
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