PIC16C55X(A)
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
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)
TMR0 timer
FEh
1
FFh
1
00h
01h
02h
T0IF bit
(INTCON<2>)
GIE bit
(INTCON<7>)
Interrupt Latency Time
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: T0IF interrupt flag is sampled here (every Q1).
2: Interrupt latency = 4Tcy, where Tcy = instruction cycle time.
3: CLKOUT is available only in RC oscillator mode.
DS40143B-page 30
Preliminary
1997 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
