AN2294 Freescale Semiconductor / Motorola, AN2294 Datasheet - Page 4

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

Software Interface
3 Software Interface
This section provides the information to initialize the USB module with the host, program the USB Device
Core (UDC) registers, and receive and transmit data. Example code and instructions to program the
registers are provided.
3.1 Initialization
To start the communication process with the host, the PLL registers within the MC68SZ328 are used to
program the 48 MHZ clock signal required by the USB module.
3.1.1 USB PLL Initialization
The USB PLL output frequency is controlled by the two USB frequency select registers shown in Figure 4
and Figure 5.
4
UPFSR1
RESET
TYPE
BIT
15
0
14
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0
UPDF[3:0]
13
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0
Figure 3. 16 MHz Crystal Configuration Hardware
USBPLL Frequency Select Register 1
12
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0
Figure 4. USBPLL Frequency Select Register 1
Freescale Semiconductor, Inc.
For More Information On This Product,
11
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0
10
0
MC68SZ328 Application Note
Go to: www.freescale.com
rw
9
0
rw
8
0
rw
7
0
0x0001
rw
6
0
rw
5
0
UMFD
CLK16MI
CLK16MO
rw
4
0
rw
3
0
0x(FF)FFF20A
rw
2
0
MOTOROLA
rw
1
0
Addr
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0
1