PIC18F258 MICROCHIP [Microchip Technology], PIC18F258 Datasheet - Page 24

• Manufacturer Part Number: PIC18F258
• Description: High Performance, 28/40-Pin Enhanced FLASH Microcontrollers with CAN
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18FXX8
If the main oscillator is configured for HS4 (PLL) mode,
an oscillator start-up time (T
time-out (T
2 ms and allows the PLL to lock to the main oscillator
frequency. A timing diagram indicating the transition
from the Timer1 oscillator to the main oscillator for HS4
mode is shown in Figure 2-9.
FIGURE 2-9:
FIGURE 2-10:
DS41159B-page 22
Internal System
(OSCCON<0>)
Internal System
(OSCCON<0>)
Note 1: T
Note 1: RC Oscillator mode assumed.
PLL Clock
Program
Counter
Program
Counter
T1OSI
OSC1
OSC2
T1OSI
Clock
OSC1
OSC2
PLL
Clock
SCS
Input
SCS
OST
) will occur. The PLL time-out is typically
= 1024 T
PC
Q4
OSC
Q3
TIMING FOR TRANSITION BETWEEN TIMER1 AND OSC1 (HS WITH PLL)
TIMING FOR TRANSITION BETWEEN TIMER1 AND OSC1 (RC, EC)
(drawing not to scale).
Q1
OST
T
OST
) plus an additional PLL
PC
Q4
T
PLL
Q1
Preliminary
T
PC + 2
OSC
1
T
1
OSC
T
If the main oscillator is configured in the RC, RCIO, EC
or ECIO modes, there is no oscillator start-up time-out.
Operation will resume after eight cycles of the main
oscillator have been counted. A timing diagram indicat-
ing the transition from the Timer1 oscillator to the main
oscillator for RC, RCIO, EC and ECIO modes is shown
in Figure 2-10.
T
1
2
2
P
3
3
PC + 2
T
4
SCS
4
T
T
T
SCS
1
5
P
5
6
6
7
7
Q1 Q2 Q3 Q4 Q1 Q2
8
 2002 Microchip Technology Inc.
8
Q1 Q2 Q3 Q4 Q1 Q2 Q3
PC + 4
PC + 4
Q3
Q4
Q4