Datasheet

© 2009 Microchip Technology Inc. DS39632E-page 391
PIC18F2455/2550/4455/4550
FIGURE 28-9: TIMER0 AND TIMER1 EXTERNAL CLOCK TIMINGS
TABLE 28-13: TIMER0 AND TIMER1 EXTERNAL CLOCK REQUIREMENTS
Note: Refer to Figure 28-4 for load conditions.
46
47
45
48
41
42
40
T0CKI
T1OSO/T13CKI
TMR0 or
TMR1
Param
No.
Symbol Characteristic Min Max Units Conditions
40 Tt0H T0CKI High Pulse Width No prescaler 0.5 T
CY + 20 — ns
With prescaler 10 — ns
41 Tt0L T0CKI Low Pulse Width No prescaler 0.5 TCY + 20 — ns
With prescaler 10 — ns
42 Tt0P T0CKI Period No prescaler T
CY + 10 — ns
With prescaler Greater of:
20 ns or
(TCY + 40)/N
—nsN = prescale
value
(1, 2, 4,..., 256)
45 Tt1H T13CKI High
Time
Synchronous, no prescaler 0.5 TCY + 20 — ns
Synchronous,
with prescaler
PIC18FXXXX 10 — ns
PIC18LFXXXX 25 — ns V
DD = 2.0V
Asynchronous PIC18FXXXX 30 — ns
PIC18LFXXXX 50 — ns VDD = 2.0V
46 Tt1L T13CKI Low
Time
Synchronous, no prescaler 0.5 T
CY + 5 — ns
Synchronous,
with prescaler
PIC18FXXXX 10 — ns
PIC18LFXXXX 25 — ns VDD = 2.0V
Asynchronous PIC18FXXXX 30 — ns
PIC18LFXXXX 50 — ns V
DD = 2.0V
47 Tt1P T13CKI Input
Period
Synchronous Greater of:
20 ns or
(TCY + 40)/N
—nsN = prescale
value (1, 2, 4, 8)
Asynchronous 60 — ns
Ft1 T13CKI Oscillator Input Frequency Range DC 50 kHz
48 Tcke2tmrI Delay from External T13CKI Clock Edge to Timer
Increment
2 T
OSC 7 TOSC —