mc9s12uf32 Freescale Semiconductor, Inc, mc9s12uf32 Datasheet - Page 117

• Manufacturer Part Number: mc9s12uf32
• Description: System Chip Guide V01.05
• Manufacturer: Freescale Semiconductor, Inc

A.4.2 Oscillator
The device features an internal Pierce oscillator. The XCLKS signal of the OSC module is tied internally
that the Pierce oscillator/external clock mode is always selected. Pierce oscillator/external clock mode
allows the input of a square wave.
.
A.4.3 USB PHY
The oscillator provides the reference clock for the USB PHY. The 12MHz oscillator clock is used for the
USB PHY to generate the 480bps USB traffic, 30MHz USB UTMI interface clock and the 60MHz internal
clock. An internal circuitry checks the generated 60MHz clock against the input 12MHz oscillator clock.
The generated 60MHz clock is assumed correct (locked) if there are exactly 15 clock cycles in 3 oscillator
clock cycles.
For the electrical characteristics of the USB PHY, please refer to Chapter 7 “Electrical” of Universal Serial
Bus Specification Revision 2.0.
Freescale Semiconductor
Conditions are shown in Table A-4 unless otherwise noted
Num C
NOTES:
1. Depending on the crystal a damping series resistor might be necessary. Also, the oscillator frequency must be 12MHz in
10
11
1
2
3
4
5
6
7
8
9
order to have the USB interface and the storage interface to work properly.
C Crystal oscillator range (Pierce)
D External square wave pulse width low
D External square wave pulse width high
D External square wave rise time
D External square wave fall time
D Input Capacitance (EXTAL, XTAL pins)
C EXTAL Pin Input Hysteresis
P Startup Current
P External square wave input frequency
P EXTAL Pin Input High Voltage
T EXTAL Pin Input High Voltage
P EXTAL Pin Input Low Voltage
T EXTAL Pin Input Low Voltage
Rating
Table A-13 Oscillator Characteristics
1
V
System on a Chip Guide — 9S12UF32DGV1/D V01.05
V
V
Symbol
V
V
HYS,EXTAL
IH,EXTAL
IH,EXTAL
IL,EXTAL
IL,EXTAL
t
t
t
t
f
i
EXTH
EXTR
f
EXTL
EXTF
OSC
C
OSC
EXT
IN
V
0.75*V
SSA
Min
100
0.5
0.5
8
8
- 0.3
DD
Typ
250
12
7
V
0.25*V
DD
Max
40
60
1
1
+ 0.3
DD
Unit
MHz
MHz
mV
pF
ns
ns
ns
ns
V
V
V
V
A
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