PIC16F87XA
FIGURE 14-2:
EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR
LP OSC
14.2 Oscillator Configurations
14.2.1 OSCILLATOR TYPES
CONFIGURATION)
The PIC16F87XA can be operated in four different
oscillator modes. The user can program two configura-
tion bits (FOSC1 and FOSC0) to select one of these
four modes:
OSC1
Clock from
Ext. System
• LP
• XT
• HS
• RC
Low Power Crystal
PIC16F87XA
OSC2
Crystal/Resonator
Open
High Speed Crystal/Resonator
Resistor/Capacitor
14.2.2
CRYSTAL OSCILLATOR/CERAMIC
RESONATORS
In XT, LP or HS modes, a crystal or ceramic resonator
is connected to the OSC1/CLKIN and OSC2/CLKOUT
pins to establish oscillation (Figure 14-1). The
PIC16F87XA oscillator design requires the use of a
parallel cut crystal. Use of a series cut crystal may give
a frequency out of the crystal manufacturers specifica-
tions. When in XT, LP or HS modes, the device can
have an external clock source to drive the OSC1/
CLKIN pin (Figure 14-2).
TABLE 14-1: CERAMIC RESONATORS
Ranges Tested:
Mode
Freq.
OSC1
OSC2
XT
455 kHz
2.0 MHz
4.0 MHz
68 - 100 pF 68 - 100 pF
15 - 68 pF
15 - 68 pF
15 - 68 pF
15 - 68 pF
HS
8.0 MHz
16.0 MHz
10 - 68 pF
10 - 22 pF
10 - 68 pF
10 - 22 pF
FIGURE 14-1:
CRYSTAL/CERAMIC
RESONATOROPERATION
(HS, XT OR LP
These values are for design guidance only.
See notes following Table 14-2.
Resonators Used:
OSC CONFIGURATION)
455 kHz Panasonic EFO-A455K04B
± 0.3%
(1)
C1
OSC1
2.0 MHz
4.0 MHz
8.0 MHz
Murata Erie CSA2.00MG
Murata Erie CSA4.00MG
Murata Erie CSA8.00MT
± 0.5%
± 0.5%
± 0.5%
± 0.5%
To
Internal
Logic
XTAL
(3)
RF
OSC2
16.0 MHz Murata Erie CSA16.00MX
SLEEP
PIC16F87XA
(2)
R
All resonators used did not have built-in capacitors.
s
(1)
C2
Note 1: See Table 14-1 and Table 14-2 for recom-
mended values of C1 and C2.
2: A series resistor (R ) may be required for AT
s
strip cut crystals.
3: RF varies with the crystal chosen.
2001 Microchip Technology Inc.
Advance Information
DS39582A-page 143
MICROCHIP [ MICROCHIP ]
