PIC16F8X_13 Datasheet, PDF (30/128 Pages) Microchip Technology – 18-pin Flash/EEPROM 8-Bit Microcontrollers

PIC16F8X
FIGURE 6-5: TIMER0 TIMING WITH EXTERNAL CLOCK
Ext. Clock Input or
Prescaler Out (Note 2)
Ext. Clock/Prescaler
Output After Sampling
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
(Note 3)
Increment TMR0 (Q4)
TMR0
T0
T0 + 1
T0 + 2
Note 1: Delay from clock input change to TMR0 increment is 3Tosc to 7Tosc. (Duration of Q = Tosc).
Therefore, the error in measuring the interval between two edges on TMR0 input =  4Tosc max.
2: External clock if no prescaler selected, Prescaler output otherwise.
3: The arrows  indicate where sampling occurs. A small clock pulse may be missed by sampling.
FIGURE 6-6: BLOCK DIAGRAM OF THE TMR0/WDT PRESCALER
CLKOUT (= Fosc/4)
RA4/T0CKI
pin
T0SE
0M
U
X
1
T0CS
1
M
0
U
X
PSA
SYNC
2
Cycles
Data Bus
8
TMR0 register
Set bit T0IF
on overflow
Watchdog
Timer
WDT Enable bit
0
M
U
1X
PSA
8-bit Prescaler
8
8 - to - 1MUX
PS2:PS0
0
1
MUX
PSA
WDT
time-out
Note: T0CS, T0SE, PSA, PS2:PS0 are bits in the OPTION_REG register.
DS30430D-page 30
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