PIC18F2450-I/ML Microchip Technology Inc., PIC18F2450-I/ML Datasheet - Page 26

• Manufacturer Part Number: PIC18F2450-I/ML
• Description: Microcontroller; 16 KB Flash; 768 RAM; 0 EEPROM; 23 I/O; 28-Pin-QFN
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F2450-I/ML

• A/d Inputs: 10-Channel, 10-Bit
• Cpu Speed: 12 MIPS
• Eeprom Memory: 0 Bytes
• Input Output: 23
• Interface: EUSART/USB
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 28-pin QFN
• Programmable Memory: 16K Bytes
• Ram Size: 768 Bytes
• Speed: 48 MHz
• Timers: 1-8-bit, 2-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

PIC18F2450/4450
2.2.1
Because of the unique requirements of the USB module,
a different approach to clock operation is necessary. In
previous PICmicro
clocks were driven by a single oscillator source; the usual
sources were primary, secondary or the internal
oscillator. With PIC18F2450/4450 devices, the primary
oscillator becomes part of the USB module and cannot
be associated to any other clock source. Thus, the USB
module must be clocked from the primary clock source;
FIGURE 2-1:
DS39760A-page 24
T1OSO
T1OSI
OSC2
OSC1
OSCILLATOR MODES AND
USB OPERATION
Primary Oscillator
Secondary Oscillator
®
devices, all core and peripheral
PIC18F2450/4450 CLOCK DIAGRAM
XT, HS, EC, ECIO
T1OSCEN
Enable
Oscillator
Sleep
Internal RC Oscillator
Advance Information
31.25 kHz
4
3
2
1
12
10
CPUDIV
6
5
4
3
2
1
PIC18F2450/4450
11
10
01
00
PLLDIV
111
110
101
100
011
010
001
000
HSPLL, ECPLL,
XTPLL, ECPIO
(4 MHz Input Only)
OSCCON<6:4>
however, the microcontroller core and other peripherals
can be separately clocked from the secondary or internal
oscillators as before.
Because of the timing requirements imposed by USB,
an internal clock of either 6 MHz or 48 MHz is required
while the USB module is enabled. Fortunately, the
microcontroller and other peripherals are not required
to run at this clock speed when using the primary
oscillator. There are numerous options to achieve the
USB module clock requirement and still provide
flexibility for clocking the rest of the device from the
primary oscillator source. These are detailed in
Section 2.3 “Oscillator Settings for USB”.
96 MHz
PLL
6
4
3
2
CPUDIV
11
10
01
00
FOSC3:FOSC0
2
Internal Oscillator
USBDIV
1
0
FOSC3:FOSC0
0
1
T1OSC
Primary
Clock
© 2006 Microchip Technology Inc.
USB Clock Source
Clock Source Option
for other Modules
WDT, PWRT, FSCM
and Two-Speed Start-up
4
Control
Clock
OSCCON<1:0>
FSEN
1
0
IDLEN
Peripherals
Peripheral
USB
CPU