PIC16F57-I/P Microchip Technology Inc., PIC16F57-I/P Datasheet - Page 24

• Manufacturer Part Number: PIC16F57-I/P
• Description: 28 PIN, 3K FLASH, 72 RAM, 20 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC16F57-I/P

• Cpu Speed: 5 MIPS
• Eeprom Memory: 0 Bytes
• Frequency: 20 MHz
• Input Output: 20
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 28-pin PDIP
• Programmable Memory: 3K Bytes
• Ram Size: 72 Bytes
• Speed: 20 MHz
• Timers: 1-8-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

PIC16F5X
4.3
Either a pre-packaged oscillator or a simple oscillator
circuit with TTL gates can be used as an external
crystal oscillator circuit. Pre-packaged oscillators
provide a wide operating range and better stability. A
well designed crystal oscillator will provide good perfor-
mance with TTL gates. Two types of crystal oscillator
circuits can be used: one with parallel resonance or one
with series resonance.
Figure 4-3 shows an implementation example of a
parallel resonant oscillator circuit. The circuit is
designed to use the fundamental frequency of the
crystal. The 74AS04 inverter performs the 180 phase
shift that a parallel oscillator requires. The 4.7 k
resistor provides the negative feedback for stability.
The 10 k
linear region. This circuit could be used for external
oscillator designs.
FIGURE 4-3:
Figure 4-4 shows a series resonant oscillator circuit.
This circuit is also designed to use the fundamental
frequency of the crystal. The inverters perform a 360
phase shift in a series resonant oscillator circuit. The
330 k resistors provide the negative feedback to bias
the inverters in their linear region.
DS41213C-page 22
10k
External Crystal Oscillator Circuit
+5V
potentiometers bias the 74AS04 in the
20 pF
10k
74AS04
XTAL
4.7k
20 pF
EXTERNAL PARALLEL
RESONANT CRYSTAL
OSCILLATOR CIRCUIT
(USING XT, HS OR LP
OSCILLATOR MODE)
10k
74AS04
Open
To Other
Devices
PIC16F5X
CLKIN
OSC2
FIGURE 4-4:
4.4
For applications where precise timing is not a require-
ment, the RC oscillator option is available. The
operation and functionality of the RC oscillator is
dependent upon a number of variables. The RC
oscillator frequency is a function of:
• Supply voltage
• Resistor (R
• Operating temperature.
The oscillator frequency will vary from unit to unit due
to normal process parameter variation. The difference
in lead frame capacitance between package types will
also affect the oscillation frequency, especially for low
C
tolerance of the external R and C components.
Figure 4-5 shows how the R/C combination is
connected.
The oscillator frequency, divided by 4, is available on
the OSC2/CLKOUT pin and can be used for test
purposes or to synchronize other logic.
FIGURE 4-5:
EXT
C
V
R
EXT
SS
74AS04
EXT
330
values. The user also needs to account for the
V
DD
K
RC Oscillator
0.1 F
EXT
XTAL
F
OSC
) and capacitor (C
/4
74AS04
330
EXTERNAL SERIES
RESONANT CRYSTAL
OSCILLATOR CIRCUIT
(USING XT, HS OR LP
OSCILLATOR MODE)
RC OSCILLATOR MODE
 2004 Microchip Technology Inc.
K
OSC2/CLKOUT
OSC1
N
74AS04
EXT
Open
To Other
Devices
) values
PIC16F5X
PIC16F5X
CLKIN
OSC2
Internal
clock