DM164120-2 Microchip Technology, DM164120-2 Datasheet - Page 31

• Manufacturer Part Number: DM164120-2
• Description: BOARD DEMO PICKIT 2 44PIN
• Manufacturer: Microchip Technology
• Type: MCUr

Specifications of DM164120-2

• Contents: 3 Boards (1 Populated, 2 Bare)
• Processor To Be Evaluated: PIC16F
• Silicon Manufacturer: Microchip
• Kit Contents: PIC16F Device, 2 PCB Boards
• Features: Small Surface Mount Prototype Area, Two Bare PCB Boards
• Development Tool Type: Hardware - Daughter Card
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: PIC16F887
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

© 2007 Microchip Technology Inc.
FIGURE 3-7:
TMR0 is a Special Function Register (SFR) and may be read or modified by the pro-
gram. The prescaler is not a SFR and thus cannot be read or modified by the program.
However, writing to TMR0 clears the prescaler.
The timer may be fed either by the same clock that drives the processor or by an exter-
nal event. Driven by the processor clock, it increments once for every instruction cycle.
This is a convenient method of marking time and is better than delay loops, as it allows
the processor to work on the problem rather than waste cycles in delay loops.
The prescaler is configured through the OPTION_REG, see Figure 3-8.
FIGURE 3-8:
Lesson 9 configures Timer0 with the prescaler for a maximum delay on Timer0. The
prescaler will divide the processor clock by 256 and Timer0 will divide that by 256
again. Thus, the Timer0 Flag will be set every 65536 μs (0.0000001 second * 256 *
256), or about 15 times a second. The main program sits in a loop waiting for the
rollover and when it does, it increments the display and then loops back.
Legend:
bit 7
Clock/4 or
T0CKI pin
X:
T0CS: Timer0 Clock Source 0 for Instruction Clock.
T0SE: Timer0 Source Edge – Don’t care when connected to instruction clock.
PSA:
PS:
X
Don’t cares – not Timer0 related.
Prescaler Assignment 0 assigns to Timer0.
Prescaler rate select ‘111’ – full prescaler, divide by 256.
Prescaler may be configured
to divide by 2, 4, 8, 16, 32, 64,
128 or 256.
X
TIMER0 SIMPLIFIED
PRESCALER CONFIGURATION THROUGH OPTION_REG
T0CS
Prescaler
44-Pin Demo Board Lessons
T0SE
PSA
TMR0
PS2
PS1
Flag set when
TMR0 overflows.
Must be cleared
in software.
DS41296B-page 27
T0IF
PS0
bit 0