PIC16F610 Datasheet, PDF (30/180 Pages) Microchip Technology – 14-Pin, Flash-Based 8-Bit CMOS Microcontrollers

PIC16F610/616/16HV610/616
3.3.4 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 3-5 shows the
external RC mode connections.
FIGURE 3-5:
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 kΩ ≤ REXT ≤ 100 kΩ, <3V
3 kΩ ≤ REXT ≤ 100 kΩ, 3-5V
CEXT > 20 pF, 2-5V
Note 1:
2:
Alternate pin functions are listed in
Section 1.0 “Device Overview”.
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.
3.4 Internal Clock Modes
The Oscillator module provides a selectable system
clock source of either 4 MHz or 8 MHz. The selectable
frequency is configured through the IOSCFS bit of the
Configuration Word.
The frequency of the internal oscillator can be can be
user-adjusted via software using the OSCTUNE
register.
3.4.1 INTOSC AND INTOSCIO MODES
The INTOSC and INTOSCIO modes configure the
internal oscillators as the system clock source when
the device is programmed using the oscillator selection
or the FOSC<2:0> bits in the Configuration Word
register (CONFIG). See Section 12.0 “Special
Features of the CPU” for more information.
In INTOSC mode, OSC1/CLKIN is available for general
purpose I/O. OSC2/CLKOUT outputs the selected
internal oscillator frequency divided by 4. The CLKOUT
signal may be used to provide a clock for external
circuitry, synchronization, calibration, test or other
application requirements.
In INTOSCIO mode, OSC1/CLKIN and OSC2/CLKOUT
are available for general purpose I/O.
DS41288C-page 28
Preliminary
© 2007 Microchip Technology Inc.