Chapter 1 Device Overview MC9S12XE-Family
MC9S12XE-Family Reference Manual Rev. 1.19
Freescale Semiconductor
75
1.3
System Clock Description
The clock and reset generator module (CRG) provides the internal clock signals for the core and all
peripheral modules.
shows the clock connections from the CRG to all modules.
Consult the CRG specification for details on clock generation.
Figure 1-9. Clock Connections
The system clock can be supplied in several ways enabling a range of system operating frequencies to be
supported:
•
The on-chip phase locked loop (PLL)
•
the PLL self clocking
•
the oscillator
The clock generated by the PLL or oscillator provides the main system clock frequencies core clock and
bus clock. As shown in
, these system clocks are used throughout the MCU to drive the core,
the memories, and the peripherals.
SCI0 . . SCI 7
SPI0 . . SPI2
IIC0 & IIC1
ATD0 & ATD1
CAN0 . . CAN4
CRG
Bus Clock
EXTAL
XTAL
Core Clock
Oscillator Clock
RAM
S12X
XGATE
FLASH &
PIT
ECT
PIM
EEE
PWM
TIM
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:
S12XE
products
in
208
MAPBGA
packages