Information

Table 25-1. OSC Signal Descriptions
Signal Description I/O
EXTAL External clock/Oscillator input I
XTAL Oscillator output O
25.5 External Crystal / Resonator Connections
The connections for a crystal/resonator frequency reference are shown in the following
figures. When using low-frequency, low-power mode, the only external component is the
crystal or ceramic resonator itself. In the other oscillator modes, load capacitors (C
x
, C
y
)
and feedback resistor (R
F
) are required. The following table shows all possible
connections.
Table 25-2. External Caystal/Resonator Connections
Oscillator Mode Connections
Low-frequency (32 kHz), low-power Connection 1
Low-frequency (32 kHz), high-gain Connection 2/Connection 3
1
High-frequency (3~32 MHz), low-power Connection 1/Connection 3
2,2
High-frequency (3~32 MHz), high-gain Connection 2/Connection 3
2
1. When the load capacitors (Cx, Cy) are greater than 30 pF, use Connection 3.
2. With the low-power mode, the oscillator has the internal feedback resistor R
F
. Therefore, the feedback resistor must not be
externally with the Connection 3.
OSC
EXTAL
Crystal or Resonator
V
SS
XTAL
Figure 25-2. Crystal/Ceramic Resonator Connections - Connection 1
Chapter 25 Oscillator (OSC)
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
Freescale Semiconductor, Inc. 467