Microchip Technology IC PIC MCU PIC16F1937-I/PT TQFP-44 MCP PIC16F1937-I/PT Data Sheet
Product codes
PIC16F1937-I/PT
2008-2011 Microchip Technology Inc.
DS41364E-page 71
PIC16(L)F1934/6/7
5.2.1.5
TIMER1 Oscillator
The Timer1 Oscillator is a separate crystal oscillator
that is associated with the Timer1 peripheral. It is opti-
mized for timekeeping operations with a 32.768 kHz
crystal connected between the T1OSO and T1OSI
device pins.
The Timer1 Oscillator can be used as an alternate sys-
tem clock source and can be selected during run-time
using clock switching. Refer to
that is associated with the Timer1 peripheral. It is opti-
mized for timekeeping operations with a 32.768 kHz
crystal connected between the T1OSO and T1OSI
device pins.
The Timer1 Oscillator can be used as an alternate sys-
tem clock source and can be selected during run-time
using clock switching. Refer to
for more information.
FIGURE 5-5:
QUARTZ CRYSTAL
OPERATION (TIMER1
OSCILLATOR)
OPERATION (TIMER1
OSCILLATOR)
5.2.1.6
External RC Mode
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.
The RC circuit connects to OSC1. OSC2/CLKOUT is
available for general purpose I/O or CLKOUT. The
function of the OSC2/CLKOUT pin is determined by the
state of the CLKOUTEN bit in Configuration Word 1.
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.
The RC circuit connects to OSC1. OSC2/CLKOUT is
available for general purpose I/O or CLKOUT. The
function of the OSC2/CLKOUT pin is determined by the
state of the CLKOUTEN bit in Configuration Word 1.
shows the external RC mode connections.
FIGURE 5-6:
EXTERNAL RC MODES
The RC oscillator frequency is a function of the supply
voltage, the resistor (R
voltage, the resistor (R
EXT
) and capacitor (C
EXT
) 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.
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.
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.
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
the V
DD
and temperature range that is
expected for the application.
3:
For oscillator design assistance, reference
the following Microchip Applications Notes:
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)
• TB097, “Interfacing a Micro Crystal
MS1V-T1K 32.768 kHz Tuning Fork
Crystal to a PIC16F690/SS
Crystal to a PIC16F690/SS
” (DS91097)
• AN1288, “Design Practices for
Low-Power External Oscillators
”
(DS01288)
C1
C2
32.768 kHz
T1OSI
To Internal
Logic
Logic
PIC
®
MCU
Crystal
T1OSO
Quartz
OSC2/CLKOUT
C
EXT
R
EXT
PIC
®
MCU
OSC1/CLKIN
F
OSC
/4 or
Internal
Clock
V
DD
V
SS
Recommended values: 10 k
R
EXT
100 k, <3V
3 k
R
EXT
100 k, 3-5V
C
EXT
> 20 pF, 2-5V
Note
1:
Output depends upon CLKOUTEN bit of the
Configuration Word 1.
Configuration Word 1.
I/O
(1)