PIC18F2420/2520/4420/4520
FIGURE 26-10:
TIMER0 AND TIMER1 EXTERNAL CLOCK TIMINGS
T0CKI
41
40
42
T1OSO/T13CKI
46
45
47
48
TMR0 or
TMR1
Note:
Refer to Figure 26-5 for load conditions.
TABLE 26-11: TIMER0 AND TIMER1 EXTERNAL CLOCK REQUIREMENTS
Param
Symbol
Characteristic
Min
Max Units Conditions
No.
40
Tt0H
T0CKI High Pulse Width
No prescaler
With prescaler
No prescaler
With prescaler
No prescaler
With prescaler
0.5 TCY + 20
10
—
—
—
—
—
—
ns
ns
ns
ns
ns
41
42
Tt0L
Tt0P
T0CKI Low Pulse Width
T0CKI Period
0.5 TCY + 20
10
TCY + 10
Greater of:
20 ns or
ns N = prescale
value
(TCY + 40)/N
(1, 2, 4,..., 256)
45
46
Tt1H
Tt1L
T13CKI
High Time
Synchronous, no prescaler
0.5 TCY + 20
—
—
—
—
—
—
—
—
—
—
—
ns
Synchronous,
with prescaler
PIC18FXXXX
10
ns
PIC18LFXXXX
25
ns VDD = 2.0V
Asynchronous PIC18FXXXX
PIC18LFXXXX
30
ns
50
ns VDD = 2.0V
T13CKI
Low Time
Synchronous, no prescaler
0.5 TCY + 5
ns
Synchronous,
with prescaler
PIC18FXXXX
10
25
30
50
ns
PIC18LFXXXX
ns VDD = 2.0V
ns
Asynchronous PIC18FXXXX
PIC18LFXXXX
ns VDD = 2.0V
47
48
Tt1P
Ft1
T13CKI
Input
Period
Synchronous
Greater of:
20 ns or
(TCY + 40)/N
ns N = prescale
value (1, 2, 4, 8)
Asynchronous
60
DC
—
50
ns
kHz
—
T13CKI Oscillator Input Frequency Range
Tcke2tmrI Delay from External T13CKI Clock Edge to
Timer Increment
2 TOSC
7 TOSC
DS39631E-page 346
© 2008 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
