AN2294 Freescale Semiconductor / Motorola, AN2294 Datasheet - Page 5

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

As these registers show, the values programmed in them control the output frequency for the USB module.
By using the Equation 1, the desired output frequency can be derived.
Where:
The corresponding input values of the UMFD to the UPFSR1 register are shown in Table 1 and Table 2 on
page 5.
MOTOROLA
UPFSR0
RESET
TYPE
BIT
15
0
Table 1. Corresponding UMFD to the UPFSR1 Register Input Values
Table 2. Corresponding UPDF to the UPFSR1 Register Input Values
F
F
(USB crystal oscillator)
UMFI = Integer of the USBPLL multiplication factor
UMFN = Numerator of the USBPLL multiplication factor
UMFD = Denominator of the USBPLL multiplication factor
UMFN = Pre-division factor of the USBPLL
14
rw
0
usbpll
usbpllin
F
usbpll
13
rw
1
UMFI
= Output frequency of USBPLL
= Output frequency of OSC16M or OSC32K + Premultiplier
12
rw
0
USBPLL Frequency Select Register 0
Figure 5. USBPLL Frequency Select Register 0
=
Freescale Semiconductor, Inc.
For More Information On This Product,
2 F
11
rw
1
×
UBRMO
usbpllin
UMFD [9:0]
UPDF[3:0]
MC68SZ328 Application Note
10
1
0
0x3FD
0x3FE
Go to: www.freescale.com
...
0
1
2
0
rw
9
0
×
UMFI
--------------------------------------------------------------------- -
rw
8
0
0x0001
+
rw
7
0
UMFN
UPDF
rw
UMFD
0x3FE
6
0
0x3FF
UPDF
...
1
2
3
1
÷
rw
5
0
(
UMFD
UMFN
rw
4
0
)
rw
3
0
Software Interface
0x(FF)FFF208
rw
2
0
rw
1
0
Eqn. 1
Addr
rw
0
1
5