MA180025 Microchip Technology, MA180025 Datasheet - Page 40

• Manufacturer Part Number: MA180025
• Description: MODULE PLUG-IN PIC18F87J90 PIM
• Manufacturer: Microchip Technology
• Series: PIC®r

Specifications of MA180025

• Accessory Type: Plug-In Module (PIM) - PIC18F87J90
• Product: Microcontroller Modules
• Silicon Manufacturer: Microchip
• Core Architecture: PIC
• Core Sub-architecture: PIC18
• Silicon Core Number: PIC18F
• Silicon Family Name: PIC18FxxJxx
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: PICDEM LCD 2 Demonstration Board (DM163030)
• For Use With: DM163030 - KIT DEV PICDEM LCD2
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

PIC18F87J90 FAMILY
3.4.2
The EC and ECPLL Oscillator modes require an
external clock source to be connected to the OSC1 pin.
There is no oscillator start-up time required after a
Power-on Reset or after an exit from Sleep mode.
In the EC Oscillator mode, the oscillator frequency
divided by 4 is available on the OSC2 pin. This signal
may be used for test purposes or to synchronize other
logic. Figure 3-3 shows the pin connections for the EC
Oscillator mode.
FIGURE 3-3:
An external clock source may also be connected to the
OSC1 pin in the HS mode, as shown in Figure 3-4. In
this configuration, the divide-by-4 output on OSC2 is
not available. Current consumption in this configuration
will be somewhat higher than EC mode, as the internal
oscillator’s feedback circuitry will be enabled (in EC
mode, the feedback circuit is disabled).
FIGURE 3-4:
3.4.3
A Phase Locked Loop (PLL) circuit is provided as an
option for users who want to use a lower frequency
oscillator circuit, or to clock the device up to its highest
rated frequency from a crystal oscillator. This may be
useful for customers who are concerned with EMI due
to high-frequency crystals, or users who require higher
clock speeds from an internal oscillator.
DS39933D-page 40
Clock from
Ext. System
Clock from
Ext. System
EXTERNAL CLOCK INPUT
(EC MODES)
PLL FREQUENCY MULTIPLIER
F
OSC
Open
/4
EXTERNAL CLOCK
INPUT OPERATION
(EC CONFIGURATION)
EXTERNAL CLOCK INPUT
OPERATION (HS OSC
CONFIGURATION)
OSC1/CLKI
OSC2/CLKO
OSC1
OSC2
PIC18F87J90
PIC18F87J90
(HS Mode)
3.4.3.1
The HSPLL and ECPLL modes provide the ability to
selectively run the device at 4 times the external
oscillating source to produce frequencies of up to
40 MHz.
The PLL is enabled by programming the FOSC<2:0>
Configuration bits to either ‘111’ (for ECPLL) or ‘101’
(for
(OSCTUNE<6>) must also be set. Clearing PLLEN
disables the PLL, regardless of the chosen oscillator
configuration. It also allows additional flexibility for
controlling the application’s clock speed in software.
FIGURE 3-5:
3.4.3.2
The PLL is also available to the internal oscillator block
when the internal oscillator block is configured as the
primary clock source. In this configuration, the PLL is
enabled in software and generates a clock output of up
to 32 MHz. The operation of INTOSC with the PLL is
described in Section 3.5.2 “INTPLL Modes”.
OSC2
OSC1
HSPLL).
HSPLL or ECPLL (CONFIG2L)
HS or EC
Mode
PLL Enable (OSCTUNE)
HSPLL and ECPLL Modes
PLL and INTOSC
In
F
F
IN
OUT
PLL BLOCK DIAGRAM
4
addition,
 2010 Microchip Technology Inc.
Comparator
Loop
Filter
Phase
VCO
the
PLLEN
SYSCLK
bit