Datasheet

 2010 Microchip Technology Inc. DS41326E-page 45
PIC16F526
8.2 Oscillator Configurations
8.2.1 OSCILLATOR TYPES
The PIC16F526 device can be operated in up to six
different oscillator modes. The user can program up to
three Configuration bits (FOSC<2:0>). To select one of
these modes:
• LP: Low-Power Crystal
• XT: Crystal/Resonator
• HS: High-Speed Crystal/Resonator
• INTRC: Internal 4/8 MHz Oscillator
• EXTRC: External Resistor/Capacitor
• EC: External High-Speed Clock Input
8.2.2 CRYSTAL OSCILLATOR/CERAMIC
RESONATORS
In HS, XT or LP modes, a crystal or ceramic resonator
is connected to the RB5/OSC1/CLKIN and RB4/OSC2/
CLKOUT pins to establish oscillation (Figure 8-1). The
PIC16F526 oscillator designs require the use of a
parallel cut crystal. Use of a series cut crystal may give
a frequency out of the crystal manufacturers
specifications. When in HS, XT or LP modes, the
device can have an external clock source drive the
RB5/OSC1/CLKIN pin (Figure 8-2). In this mode, the
output drive levels on the OSC2 pin are very weak. If
the part is used in this fashion, then this pin should be
left open and unloaded. Also when using this mode, the
external clock should observe the frequency limits for
the Clock mode chosen (HS, XT or LP).
FIGURE 8-1: CRYSTAL OPERATION
(OR CERAMIC
RESONATOR)
(HS, XT OR LP OSC
CONFIGURATION)
FIGURE 8-2: EXTERNAL CLOCK INPUT
OPERATION (HS, XT, LP
OR EC OSC
CONFIGURATION)
TABLE 8-1: CAPACITOR SELECTION FOR
CERAMIC RESONATORS
Note 1: This device has been designed to per-
form to the parameters of its data sheet.
It has been tested to an electrical
specification designed to determine its
conformance with these parameters.
Due to process differences in the
manufacture of this device, this device
may have different performance charac-
teristics than its earlier version. These
differences may cause this device to
perform differently in your application
than the earlier version of this device.
2: The user should verify that the device
oscillator starts and performs as
expected. Adjusting the loading capacitor
values and/or the Oscillator mode may
be required.
Osc
Type
Resonator
Freq.
Cap. Range
C1
Cap. Range
C2
XT 4.0 MHz 30 pF 30 pF
HS 16 MHz 10-47 pF 10-47 pF
Note 1: These values are for design guidance
only. Since each resonator has its own
characteristics, the user should consult
the resonator manufacturer for
appropriate values of external
components.
Note 1: See Capacitor Selection tables for
recommended values of C1 and C2.
2: A series resistor (RS) may be required for AT
strip cut crystals.
3: RF approx. value = 10 M.
C1
(1)
C2
(1)
XTAL
OSC2
OSC1
RF
(3)
Sleep
To internal
logic
RS
(2)
PIC16F526
Clock From
ext. system
PIC16F526
OSC2/CLKOUT/RB4
RB5/OSC1/CLKIN
OSC2/CLKOUT/RB4
(1)
EC, HS, XT, LP
Note 1: RB4 is available in EC mode only.