AN2294 Freescale Semiconductor / Motorola, AN2294 Datasheet - Page 7

• Manufacturer Part Number: AN2294
• Description: MC68SZ328 USB Configuration Setup Application Note
• Manufacturer: Freescale Semiconductor / Motorola

The results are 192 MHz. However, because USBCDIV / 4 (CSCR bit 13-11) the USB_CLK output
frequency will be 48 MHz. Refer to the Code Example 1 on page 8 for more information on programming
the USBPLL registers.
System Configuration for the 32.768 kHz Crystal
System Configuration for the 16 MHz Crystal
MOTOROLA
1. Set the value of CSCR register to 0x4C04 using the following:
2. Set the values of UMFN, UMFI, UPDF, and UMFD in the two frequency select registers:
3. Set the value of CSCR after the previous registers are initialized to equal 0x4C03.
1. Set the value of the CSCR register to 0xCC0C by enabling the following:
2. Set the values of UMFN, UMFI, UPDF, and UMFD in the two frequency select registers:
3. CSCR remains the same because the system clock has already been enabled.
— Consider the premultiplier output (512 *32.768 KHz)
— Enable USBPLL
— Set USBCLK / 4
— Set MCUPLL_CLK /1
— Disable the internal clock
— Enable the USB clock
UPFSR0—0x2969
UPFSR1—0x01F3
PLLCR—0x6400
The system is now setup to use the system clock.
— 16 MHz external clock
— USBPLL
— Internal clock
— USB clock
UPFSR0—0x3400
UPFSR1—0x0000
PLLCR—0x6400
Freescale Semiconductor, Inc.
For More Information On This Product,
MC68SZ328 Application Note
Go to: www.freescale.com
Software Interface
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