PIC16C71X
FIGURE 6-3: TIMER0 TIMING: INTERNAL CLOCK/PRESCALE 1:2
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
(Program
Counter)
PC-1
PC
PC+1
PC+2
PC+3
PC+4
PC+5
PC+6
MOVF TMR0,W MOVF TMR0,W MOVF TMR0,W MOVF TMR0,W MOVF TMR0,W
MOVWF TMR0
Instruction
Fetch
T0
T0+1
NT0+1
PC+6
NT0
TMR0
Instruction
Execute
Read TMR0
reads NT0
Read TMR0
reads NT0
Read TMR0
reads NT0
Read TMR0
reads NT0
Read TMR0
reads NT0 + 1
Write TMR0
executed
FIGURE 6-4: TIMER0 INTERRUPT TIMING
Q1 Q2 Q3
Q4
Q1 Q2 Q3
Q4
Q1 Q2 Q3
Q4
Q1 Q2 Q3
Q4
Q1 Q2 Q3
Q4
OSC1
CLKOUT(3)
Timer0
FEh
FFh
00h
01h
02h
1
1
T0IF bit
(INTCON<2>)
GIE bit
(INTCON<7>)
INSTRUCTION
FLOW
PC
PC
PC +1
PC +1
0004h
0005h
Instruction
fetched
Inst (PC)
Inst (PC+1)
Inst (0004h)
Inst (0005h)
Instruction
executed
Inst (PC-1)
Dummy cycle
Dummy cycle
Inst (0004h)
Inst (PC)
Note 1: Interrupt flag bit T0IF is sampled here (every Q1).
2: Interrupt latency = 4Tcy where Tcy = instruction cycle time.
3: CLKOUT is available only in RC oscillator mode.
DS30272A-page 32
1997 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
