Datasheet

Table Of Contents
PIC16(L)F1508/9
DS40001609C-page 50 2011-2013 Microchip Technology Inc.
FIGURE 5-3: QUARTZ CRYSTAL
OPERATION (LP, XT OR
HS MODE)
FIGURE 5-4: CERAMIC RESONATOR
OPERATION
(XT OR HS MODE)
5.2.1.3 Oscillator Start-up Timer (OST)
If the oscillator module is configured for LP, XT or HS
modes, the Oscillator Start-up Timer (OST) counts
1024 oscillations from OSC1. This occurs following a
Power-On Reset (POR) and when the Power-up Timer
(PWRT) has expired (if configured), or a wake-up from
Sleep. During this time, the program counter does not
increment and program execution is suspended,
unless either FSCM or Two-Speed Start-Up are
enabled. In this case, code will continue to execute at
the selected INTOSC frequency while the OST is
counting. The OST ensures that the oscillator circuit,
using a quartz crystal resonator or ceramic resonator,
has started and is providing a stable system clock to
the oscillator module.
In order to minimize latency between external oscillator
start-up and code execution, the Two-Speed Clock
Start-up mode can be selected (see Section 5.4
“Two-Speed Clock Start-up Mode”).
Note 1: Quartz crystal characteristics vary
according to type, package and
manufacturer. The user should consult the
manufacturer data sheets for specifications
and recommended application.
2: Always verify oscillator performance over
the V
DD and temperature range that is
expected for the application.
3: For oscillator design assistance, reference
the following Microchip Applications Notes:
• AN826, “Crystal Oscillator Basics and
Crystal Selection for rfPIC
®
and PIC
®
Devices” (DS00826)
• AN849, “Basic PIC
®
Oscillator Design
(DS00849)
• AN943, “Practical PIC
®
Oscillator
Analysis and Design” (DS00943)
• AN949, “Making Your Oscillator Work
(DS00949)
RS
(1)
OSC1/CLKIN
PIC
®
MCU
OSC2/CLKOUT
Note 1: A series resistor (Rs) may be required for
quartz crystals with low drive level.
2: The value of R
F varies with the Oscillator mode
selected (typically between 2 MΩ and 10 ).
RF
(2)
C2
C1
To Internal
Logic
Sleep
Quartz
Crystal
Rev. 10-000059A
7/30/2013
RS
(1)
OSC1/CLKIN
PIC
®
MCU
OSC2/CLKOUT
Note 1: A series resistor (Rs) may be required for
ceramic resonators with low drive level.
2: The value of R
F varies with the Oscillator mode
selected (typically between 2 MΩ and 10 ).
3. An additional parallel feedback resistor (R
P)
may be required for proper ceramic resonator
operation.
RF
(2)
C2
C1
To Internal
Logic
Sleep
RP
(3)
Ceramic
Resonator
Rev. 10-000060A
7/30/2013