Datasheet

© 2009 Microchip Technology Inc. DS39689F-page 9
PIC18F2221/2321/4221/4321 FAMILY
1.0 DEVICE OVERVIEW
This document contains device specific information for
the following devices:
This family offers the advantages of all PIC18 micro-
controllers – namely, high computational performance at
an economical price – with the addition of high-
endurance, Enhanced Flash program memory. On top of
these features, the PIC18F2221/2321/4221/4321 family
introduces design enhancements that make these micro-
controllers a logical choice for many high-performance,
power sensitive applications.
1.1 New Core Features
1.1.1 nanoWatt TECHNOLOGY
All of the devices in the PIC18F2221/2321/4221/4321
family incorporate a range of features that can signifi-
cantly reduce power consumption during operation.
Key items include:
• Alternate Run Modes: By clocking the controller
from the Timer1 source or the internal oscillator
block, power consumption during code execution
can be reduced by as much as 90%.
• Multiple Idle Modes: The controller can also run
with its CPU core disabled but the peripherals still
active. In these states, power consumption can be
reduced even further, to as little as 4% of normal
operation requirements.
• On-the-Fly Mode Switching: The
power-managed modes are invoked by user code
during operation, allowing the user to incorporate
power-saving ideas into their application’s
software design.
• Low Consumption in Key Modules: The
power requirements for both Timer1 and the
Watchdog Timer are minimized. See
Section 27.0 “Electrical Characteristics” for
values.
1.1.2 MULTIPLE OSCILLATOR OPTIONS
AND FEATURES
All of the devices in the PIC18F2221/2321/4221/4321
family offer ten different oscillator options, allowing
users a wide range of choices in developing application
hardware. These include:
• Four Crystal modes, using crystals or ceramic
resonators.
• Two External Clock modes, offering the option of
using two pins (oscillator input and a divide-by-4
clock output) or one pin (oscillator input, with the
second pin reassigned as general I/O).
• Two External RC Oscillator modes with the same
pin options as the External Clock modes.
• Two Internal Oscillator modes which provide
an 8 MHz clock and an INTRC source
(approximately 31 kHz), as well as a range of
6 user-selectable clock frequencies, between
125 kHz to 4 MHz, for a total of 8 clock frequencies.
One or both of the oscillator pins can be used for
general purpose I/O.
• A Phase Lock Loop (PLL) frequency multiplier,
available to both the high-speed crystal and
internal oscillator modes, which allows clock
speeds of up to 40 MHz. Used with the internal
oscillator, the PLL gives users a complete selection
of clock speeds, from 31 kHz to 32 MHz – all
without using an external crystal or clock circuit.
Besides its availability as a clock source, the internal
oscillator block provides a stable reference source that
gives the family additional features for robust
operation:
• Fail-Safe Clock Monitor: This option constantly
monitors the main clock source against a reference
signal provided by the internal oscillator. If a clock
failure occurs, the controller is switched to the
internal oscillator block, allowing for continued
low-speed operation or a safe application
shutdown.
• Two-Speed Start-up: This option allows the
internal oscillator to serve as the clock source
from Power-on Reset, or wake-up from Sleep
mode, until the primary clock source is available.
• PIC18F2221 • PIC18LF2221
• PIC18F2321 • PIC18LF2321
• PIC18F4221 • PIC18LF4221
• PIC18F4321 • PIC18LF4321