PIC16F8X_13 Datasheet, PDF (28/128 Pages) Microchip Technology – 18-pin Flash/EEPROM 8-Bit Microcontrollers

PIC16F8X
FIGURE 6-3: TMR0 TIMING: INTERNAL CLOCK/PRESCALE 1:2
PC
Instruction
Fetch
TMR0
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
PC-1
PC
PC+1
PC+2
PC+3
PC+4
PC+5
MOVWF TMR0 MOVF TMR0,W MOVF TMR0,W MOVF TMR0,W MOVF TMR0,W MOVF TMR0,W
PC+6
T0
T0+1
NT0
NT0+1
Instruction
Execute
Write TMR0
executed
Read TMR0
reads NT0
Read TMR0
reads NT0
Read TMR0
reads NT0
Read TMR0
reads NT0
Read TMR0
reads NT0 + 1
FIGURE 6-4: TMR0 INTERRUPT TIMING
OSC1
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
CLKOUT⁽³⁾
TMR0 timer
FEh
FFh
00h
01h
02h
T0IF bit ⁴
1
1
(INTCON<2>)
GIE bit
(INTCON<7>)
INSTRUCTION FLOW
PC
PC
Instruction
fetched
Inst (PC)
Instruction
executed
Inst (PC-1)
PC +1
Inst (PC+1)
Inst (PC)
Interrupt Latency⁽²⁾
PC +1
Dummy cycle
0004h
Inst (0004h)
Dummy cycle
0005h
Inst (0005h)
Inst (0004h)
Note 1: T0IF interrupt flag is sampled here (every Q1).
2: Interrupt latency = 3.25Tcy, where Tcy = instruction cycle time.
3: CLKOUT is available only in RC oscillator mode.
4: The timer clock (after the synchronizer circuit) which increments the timer from FFh to 00h immediately sets the T0IF bit.
The TMR0 register will roll over 3 Tosc cycles later.
DS30430D-page 28
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