Datasheet

PIC16F872
DS30221C-page 130 © 2006 Microchip Technology Inc.
FIGURE 14-8: TIMER0 AND TIMER1 EXTERNAL CLOCK TIMINGS
TABLE 14-4: TIMER0 AND TIMER1 EXTERNAL CLOCK REQUIREMENTS
Param
No.
Symbol Characteristic Min Typ† Max Units Conditions
40* Tt0H T0CKI High Pulse Width No Prescaler 0.5T
CY + 20 — — ns Must also meet
parameter 42
With Prescaler 10 — — ns
41* Tt0L T0CKI Low Pulse Width No Prescaler 0.5T
CY + 20 — — ns Must also meet
parameter 42
With Prescaler 10 — — ns
42* Tt0P T0CKI Period No Prescaler T
CY + 40 — — ns
With Prescaler Greater of:
20 or T
CY + 40
N
— — ns N = prescale
value (2, 4,...,
256)
45* Tt1H T1CKI High Time Synchronous, Prescaler = 1 0.5T
CY + 20 — — ns Must also meet
parameter 47
Synchronous,
Prescaler = 2,4,8
Standard(F)15——ns
Extended(LF)25 ——ns
Asynchronous Standard(F)30——ns
Extended(LF)50 ——ns
46* Tt1L T1CKI Low Time Synchronous, Prescaler = 1 0.5T
CY + 20 — — ns Must also meet
parameter 47
Synchronous,
Prescaler = 2,4,8
Standard(F)15——ns
Extended(LF)25 ——ns
Asynchronous Standard(F)30——ns
Extended(LF)50 ——ns
47* Tt1P T1CKI Input
Period
Synchronous Standard(F) Greater of:
30
OR TCY + 40
N
— — ns N = prescale
value (1, 2, 4, 8)
Extended(LF) Greater of:
50
OR TCY + 40
N
N = prescale
value (1, 2, 4, 8)
Asynchronous Standard(F)60——ns
Extended(LF) 100 — — ns
Ft1 Timer1 Oscillator Input Frequency Range
(oscillator enabled by setting bit T1OSCEN)
DC — 200 kHz
48 TCKEZtmr1 Delay from External Clock Edge to Timer Increment 2T
OSC —7TOSC —
* These parameters are characterized but not tested.
† Data in "Typ" column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only and are not tested.
Note: Refer to Figure 14-3 for load conditions.
46
47
45
48
41
42
40
RA4/T0CKI
RC0/T1OSO/T1CKI
TMR0 or
TMR1