DM163035+TEFLCST3 Microchip Technology, DM163035+TEFLCST3 Datasheet - Page 79

• 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

© 2009 Microchip Technology Inc.
3.2.6
3.2.6.1
To configure the peripherals used in this lab, the following registers are used:
1. Comparator 2 Control Register 0: CM2CON0 (Register 8-2 in Section 8.0 of the
2. Timer0 Result Register: TMR0 (Section 5.0 of the PIC16F690 data sheet)
3.2.6.2
This lab expands on concepts discussed in the first comparator lab by implementing
intelligence to create a higher resolution temperature sensor measurement application.
Comparator 2 will be configured to operate as a simple relaxation oscillator with the
addition of a few external components. The non-inverting reference will be connected
to a variable voltage divider connected to the C2IN+ pin on the PIC16F690.
The basic oscillator circuit is shown in Figure 3-10.
FIGURE 3-10:
Referring to Figure 3-10, at start-up, the capacitor connected to the inverting reference
of Comparator 2 is completely discharged. Therefore, the voltage present on the
inverting reference is 0V, which is less than the voltage on the non-inverting reference
and Comparator 2’s output goes high. This rapidly charges the capacitor through the
diode (D1) to a level approximately equal to V
the inverting reference input is greater than the non-inverting reference voltage, the
output transitions low. The charge across the capacitor then discharges slowly across
the resistor R1. Once the capacitor charge drops below the voltage on the
non-inverting reference, the cycle repeats and the system oscillates. The frequency of
this oscillation is dependant on the RC time constant (τ = R x C), or the time it takes to
- Same functionality as CM1CON0 outlined at the beginning of this chapter.
- This 8-bit register increments on edge-transitions of the internal instruction
PIC16F690 data sheet)
clock (F
(T0CKI).
R
R
3
2
V
V
Lab 3 Higher Resolution Sensor Readings Using a Single
Comparator
NEW REGISTERS USED IN THIS LAB
OVERVIEW
DD
OSC
V
SS
/4) or an external clock source on the Timer0 Clock Input pin
BASIC RELAXATION OSCILLATOR CIRCUIT
t
R
1
V
C12IN0-
SS
C2IN+
PIC16F690
V
Comparator Peripheral
SS
C
1
+
_
DD
. Once the Comparator detects that
C2OUT
D1
V
DS41381A-page 75
t