MC9S12UF32 Datasheet, PDF (117/128 Pages) Freescale Semiconductor, Inc – System on a Chip Guide V01.05

System on a Chip Guide — 9S12UF32DGV1/D V01.05
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.
.
Table A-13 Oscillator Characteristics
Conditions are shown in Table A-4 unless otherwise noted
Num C
Rating
Symbol
Min
Typ
Max
Unit
1 C _{Crystal oscillator range (Pierce)} ¹
f_OSC
0.5
12
40
MHz
2 P Startup Current
i_OSC
100
µA
3 P External square wave input frequency
f_EXT
0.5
60
MHz
4 D External square wave pulse width low
t_EXTL
8
ns
5 D External square wave pulse width high
t_EXTH
8
ns
6 D External square wave rise time
t_EXTR
1
ns
7 D External square wave fall time
t_EXTF
1
ns
8 D Input Capacitance (EXTAL, XTAL pins)
C_IN
7
pF
9 P EXTAL Pin Input High Voltage
V_IH,EXTAL 0.75*V_DD
V
T EXTAL Pin Input High Voltage
V_IH,EXTAL
V_DD + 0.3
V
10 P EXTAL Pin Input Low Voltage
V_IL,EXTAL
0.25*V_DD
V
T EXTAL Pin Input Low Voltage
V_IL,EXTAL V_SSA - 0.3
V
11 C EXTAL Pin Input Hysteresis
V_HYS,EXTAL
250
mV
NOTES:
1. Depending on the crystal a damping series resistor might be necessary. Also, the oscillator frequency must be 12MHz in
order to have the USB interface and the storage interface to work properly.
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
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