PCM18XT0 Microchip Technology, PCM18XT0 Datasheet - Page 30

• Manufacturer Part Number: PCM18XT0
• Description: MODULE PROC PIC18F4685
• Manufacturer: Microchip Technology

Specifications of PCM18XT0

• Accessory Type: Processor Module
• Product: Microcontroller Modules
• Core Processor: PIC18F4685
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• For Use With/related Products: ICE2000
• For Use With: ICE2000 - EMULATOR MPLAB-ICE 2000 POD
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Not applicable / Not applicable

PIC18F2682/2685/4682/4685
2.7
Like previous PIC18 devices, the PIC18F2682/2685/
4682/4685 family includes a feature that allows the
device clock source to be switched from the main
oscillator to an alternate low-frequency clock source.
PIC18F2682/2685/4682/4685 devices offer two alter-
nate clock sources. When an alternate clock source is
enabled, the various power-managed operating modes
are available.
Essentially, there are three clock sources for these
devices:
• Primary oscillators
• Secondary oscillators
• Internal oscillator block
The primary oscillators include the External Crystal
and Resonator modes, the External RC modes, the
External Clock modes and the internal oscillator block.
The particular mode is defined by the FOSC3:FOSC0
Configuration bits. The details of these modes are
covered earlier in this chapter.
FIGURE 2-8:
DS39761C-page 30
T1OSO
T1OSI
OSC2
OSC1
Clock Sources and Oscillator
Switching
Primary Oscillator
Secondary Oscillator
PIC18F2682/2685/4682/4685 CLOCK DIAGRAM
OSCCON<6:4>
Oscillator
Internal
Source
Source
INTRC
8 MHz
Block
Sleep
T1OSCEN
Enable
Oscillator
31 kHz (INTRC)
(INTOSC)
8 MHz
OSCTUNE<6>
PIC18F2682/2685/4682/4685
1
0
500 kHz
250 kHz
125 kHz
31 kHz
8 MHz
4 MHz
2 MHz
1 MHz
OSCCON<6:4>
register details.
The secondary oscillators are those external sources
not connected to the OSC1 or OSC2 pins. These
sources may continue to operate even after the
controller is placed in a power-managed mode.
PIC18F2682/2685/4682/4685 devices offer the Timer1
oscillator as a secondary oscillator. In all power-
managed modes, this oscillator is often the time base
for functions such as a Real-Time Clock.
Most often, a 32.768 kHz watch crystal is connected
between the RC0/T1OSO/T13CKI and RC1/T1OSI
pins. Like the LP mode oscillator circuit, loading
capacitors are also connected from each pin to ground.
The Timer1 oscillator is discussed in greater detail in
Section 12.3 “Timer1 Oscillator”.
In addition to being a primary clock source, the internal
oscillator block is available as a power-managed
mode clock source. The INTRC source is also used as
the clock source for several special features, such as
the WDT and Fail-Safe Clock Monitor.
The clock sources for the PIC18F2682/2685/4682/4685
devices are shown in Figure 2-8. See Section 24.0
“Special Features of the CPU” for Configuration
OSCTUNE<7>
111
110
101
100
011
010
001
000
4 x PLL
HSPLL, INTOSC/PLL
LP, XT, HS, RC, EC
Internal Oscillator
FOSC3:FOSC0
T1OSC
© 2009 Microchip Technology Inc.
Clock Source Option
for other Modules
WDT, PWRT, FSCM
and Two-Speed Startup
Control
Clock
OSCCON<1:0>
Peripherals
IDLEN
CPU