PIC16F722AT-ISS Datasheet, PDF (82/286 Pages) Microchip Technology – 28-Pin Flash Microcontrollers with nanoWatt XLP Technology

PIC16(L)F722A/723A
FIGURE 7-4:
CERAMIC RESONATOR
OPERATION
(XT OR HS MODE)
PIC^® MCU
OSC1/CLKIN
C1
To Internal
Logic
RP⁽³⁾
RF⁽²⁾
Sleep
C2 _{Ceramic RS}⁽¹⁾
Resonator
OSC2/CLKOUT
Note 1: A series resistor (RS) may be required for
ceramic resonators with low drive level.
2: The value of RF varies with the Oscillator mode
selected.
3: An additional parallel feedback resistor (RP)
may be required for proper ceramic resonator
operation.
7.6.4 EXTERNAL RC MODES
The external Resistor-Capacitor (RC) modes support
the use of an external RC circuit. This allows the
designer maximum flexibility in frequency choice while
keeping costs to a minimum when clock accuracy is not
required. There are two modes: RC and RCIO.
In RC mode, the RC circuit connects to OSC1. OSC2/
CLKOUT outputs the RC oscillator frequency divided
by 4. This signal may be used to provide a clock for
external circuitry, synchronization, calibration, test or
other application requirements. Figure 7-5 shows the
external RC mode connections.
FIGURE 7-5:
EXTERNAL RC MODES
VDD
REXT
CEXT
VSS
FOSC/4 or
I/O⁽²⁾
PIC^® MCU
OSC1/CLKIN
Internal
Clock
OSC2/CLKOUT⁽¹⁾
Recommended values: 10 k  REXT  100 k, <3V
3 k  REXT  100 k, 3-5V
CEXT > 20 pF, 2-5V
Note 1:
2:
Alternate pin functions are described in
Section 6.1 “Alternate Pin Function”.
Output depends upon RC or RCIO clock mode.
In RCIO mode, the RC circuit is connected to OSC1.
OSC2 becomes an additional general purpose I/O pin.
The RC oscillator frequency is a function of the supply
voltage, the resistor (REXT) and capacitor (CEXT) values
and the operating temperature. Other factors affecting
the oscillator frequency are:
• threshold voltage variation
• component tolerances
• packaging variations in capacitance
The user also needs to take into account variation due
to tolerance of external RC components used.
TABLE 7-1: SUMMARY OF REGISTERS ASSOCIATED WITH CLOCK SOURCES
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Register
on Page
OSCCON
—
—
IRCF1 IRCF0 ICSL
ICSS
—
—
79
OSCTUNE
—
—
TUN5 TUN4 TUN3 TUN2 TUN1 TUN0
80
Legend: x = unknown, u = unchanged, – = unimplemented locations read as ‘0’. Shaded cells are not used by
oscillators.
TABLE 7-2: SUMMARY OF CONFIGURATION WORD WITH CLOCK SOURCES
Name Bits Bit -/7
Bit -/6
Bit 13/5
Bit 12/4
Bit 11/3
Bit 10/2
Bit 9/1
Bit 8/0
CONFIG1
Legend:
13:8
—
—
DEBUG
PLLEN
—
BORV BOREN1
7:0
—
CP
MCLRE
PWRTE
WDTE
FOSC<2:0>
— = unimplemented location, read as ‘0’. Shaded cells are not used by clock sources.
BOREN0
Register
on Page
83
DS41417B-page 82
 2010-2012 Microchip Technology Inc.