start-up. The crystal and associated components should be mounted as near as possible to the EXTAL and
XTAL pins to minimize output distortion and start-up stabilization time.
Crystal Frequency = 4 - 8MHz (optimized for 8MHz)
EXTAL XTAL EXTAL XTAL
Sample External Crystal Parameters:
Rz = 750 KΩ
RZ
RZ
Note: If the operating temperature range is limited to
CLKMODE = 0
below 85oC (105oC junction), then Rz = 10 Meg Ω
CL1
CL2
Figure 3-2 Connecting to a Crystal Oscillator
Note:
The OCCS_COHL bit must be set to 1 when a crystal oscillator is used. The reset condition on the
OCCS_COHL bit is 0. Please see the COHL bit in the Oscillator Control (OSCTL) register, discussed
in the 56F8300 Peripheral User Manual.
3.2.2
Ceramic Resonator (Default)
It is also possible to drive the internal oscillator with a ceramic resonator, assuming the overall system
design can tolerate the reduced signal integrity. A typical ceramic resonator circuit is shown in Figure 3-3.
Refer to the supplier’s recommendations when selecting a ceramic resonator and associated components.
The resonator and components should be mounted as near as possible to the EXTAL and XTAL pins.
Resonator Frequency = 4 - 8MHz (optimized for 8MHz)
3 Terminal
2 Terminal
Sample External Ceramic Resonator Parameters:
Rz = 750 KΩ
EXTAL XTAL
RZ
EXTAL XTAL
RZ
CLKMODE = 0
CL1
CL2
C1
C2
Figure 3-3 Connecting a Ceramic Resonator
Note:
The OCCS_COHL bit must be set to 0 when a ceramic resonator is used. The reset condition on the
OCCS_COHL bit is 0. Please see the COHL bit in the Oscillator Control (OSCTL) register, discussed
in the 56F8300 Peripheral User Manual.
3.2.3
External Clock Source
The recommended method of connecting an external clock is given in Figure 3-4. The external clock
source is connected to XTAL and the EXTAL pin is grounded. When using an external clock source, set
56F8367 Technical Data, Rev. 9
40
Freescale Semiconductor
Preliminary
FREESCALE [ Freescale ]
