PIC18F4550-I/PT Microchip Technology Inc., PIC18F4550-I/PT Datasheet - Page 31

• Manufacturer Part Number: PIC18F4550-I/PT
• Description: 44 PIN, 32 KB FLASH, 2048 RAM, FS-USB 2.0
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F4550-I/PT

• A/d Inputs: 13-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 12 MIPS
• Eeprom Memory: 256 Bytes
• Input Output: 34
• Interface: I2C/SPI/UART/USART/USB
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 44-pin TQFP
• Programmable Memory: 32K Bytes
• Ram Size: 2K Bytes
• Speed: 48 MHz
• Timers: 1-8-bit, 3-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

2.3
When the PIC18F4550 is used for USB connectivity, it
must have either a 6 MHz or 48 MHz clock for USB
operation, depending on whether Low-Speed or
Full-Speed mode is being used. This may require some
forethought in selecting an oscillator frequency and
programming the device.
The full range of possible oscillator configurations
compatible with USB operation is shown in Table 2-3.
2.3.1
The USB clock for Low-Speed mode is derived from
the primary oscillator chain and not directly from the
PLL. It is divided by 4 to produce the actual 6 MHz
clock. Because of this, the microcontroller can only use
a clock frequency of 24 MHz when the USB module is
TABLE 2-3:
© 2006 Microchip Technology Inc.
Legend:
Note 1:
Input Oscillator
Frequency
48 MHz
48 MHz
40 MHz
24 MHz
Oscillator Settings for USB
All clock frequencies, except 24 MHz, are exclusively associated with full-speed USB operation (USB clock of 48 MHz).
Bold is used to highlight clock selections that are compatible with low-speed USB operation (system clock of 24 MHz,
USB clock of 6 MHz).
Only valid when the USBDIV Configuration bit is cleared.
LOW-SPEED OPERATION
OSCILLATOR CONFIGURATION OPTIONS FOR USB OPERATION
(PLLDIV2:PLLDIV0)
PLL Division
12 (111)
10 (110)
6 (101)
N/A
(1)
PIC18F2455/2550/4455/4550
HSPLL, ECPLL, ECPIO
Preliminary
(FOSC3:FOSC0)
ECPLL, ECPIO
ECPLL, ECPIO
HS, EC, ECIO
Clock Mode
EC, ECIO
EC, ECIO
EC, ECIO
active and the controller clock source is one of the
primary oscillator modes (XT, HS or EC, with or without
the PLL).
This restriction does not apply if the microcontroller
clock source is the secondary oscillator or internal
oscillator block.
2.3.2
The USB module, in either mode, can run asynchro-
nously with respect to the microcontroller core and
other peripherals. This means that applications can use
the primary oscillator for the USB clock while the micro-
controller runs from a separate clock source at a lower
speed. If it is necessary to run the entire application
from only one clock source, full-speed operation
provides a greater selection of microcontroller clock
frequencies.
(CPUDIV1:CPUDIV0)
MCU Clock Division
RUNNING DIFFERENT USB AND
MICROCONTROLLER CLOCKS
None (00)
None (00)
None (00)
None (00)
2 (01)
3 (10)
4 (11)
2 (01)
3 (10)
4 (11)
2 (00)
3 (01)
4 (10)
6 (11)
2 (01)
3 (10)
4 (11)
2 (00)
3 (01)
4 (10)
6 (11)
2 (01)
3 (10)
4 (11)
2 (00)
3 (01)
4 (10)
6 (11)
Clock Frequency
Microcontroller
DS39632C-page 29
13.33 MHz
48 MHz
24 MHz
16 MHz
12 MHz
48 MHz
24 MHz
16 MHz
12 MHz
48 MHz
32 MHz
24 MHz
16 MHz
40 MHz
20 MHz
10 MHz
48 MHz
32 MHz
24 MHz
16 MHz
24 MHz
12 MHz
48 MHz
32 MHz
24 MHz
16 MHz
8 MHz
6 MHz