XC2200 Derivatives
System Units (Vol. 1 of 2)
System Control Unit (SCU)
User’s Manual
6-15
V2.1, 2008-08
SCU, V1.13
6.1.5
Clock Control Unit
The Clock Control Unit (CCU) selects the current clock sources for the clock signals
used in the XC2200. It generates the following clocks:
•
System clock
f
SYS
•
RTC count clock
f
RTC
•
Output clock
f
EXT
The following clock signals can be selected:
•
PLL clock
f
PLL
•
The oscillator clock (OSC_HP)
f
OSC
•
Wake-up clock
f
WU
•
Input CLKIN1 as Direct Clock Input
f
CLKIN1
•
Input CLKIN2 as Direct Clock Input
f
CLKIN2
6.1.5.1
Clock Generation
Different clock sources can be selected for the generated clock signals.
Note: The selected clock sources are affected by the start-up procedure. See chapter
Device Status after Start-up for the register values set by the different start-up
procedures.
System Clock Generation
The system clock
f
SYS
can be selected from the following clock sources in the CCU:
•
Wake-up clock
f
WU
•
The oscillator clock (OSC_HP)
f
OSC
•
PLL clock
f
PLL
•
Input CLKIN1 as Direct Clock Input
f
CLKIN1
