Datasheet

PIC16(L)F1516/7/8/9
DS41452C-page 50  2010-2012 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)
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 M to 10 M.
C1
C2
Quartz
R
S
(1)
OSC1/CLKIN
RF
(2)
Sleep
To Internal
Logic
PIC
®
MCU
Crystal
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 M to 10 M.
3: An additional parallel feedback resistor (R
P)
may be required for proper ceramic resonator
operation.
C1
C2
Ceramic
R
S
(1)
OSC1/CLKIN
RF
(2)
Sleep
To Internal
Logic
PIC
®
MCU
RP
(3)
Resonator
OSC2/CLKOUT