saf-xc866-4rri3v Infineon Technologies Corporation, saf-xc866-4rri3v Datasheet - Page 61

• Manufacturer Part Number: saf-xc866-4rri3v
• Description: 8-bit Single-chip Microcontroller
• Manufacturer: Infineon Technologies Corporation

3.8
The Clock Generation Unit (CGU) allows great flexibility in the clock generation for the
XC866. The power consumption is indirectly proportional to the frequency, whereas the
performance of the microcontroller is directly proportional to the frequency. During user
program execution, the frequency can be programmed for an optimal ratio between
performance and power consumption. Therefore the power consumption can be
adapted to the actual application state.
Features:
• Phase-Locked Loop (PLL) for multiplying clock source by different factors
• PLL Base Mode
• Prescaler Mode
• PLL Mode
• Power-down mode support
The CGU consists of an oscillator circuit and a PLL.In the XC866, the oscillator can be
from either of these two sources: the on-chip oscillator (10 MHz) or the external oscillator
(4 MHz to 12 MHz). The term “oscillator” is used to refer to both on-chip oscillator and
external oscillator, unless otherwise stated. After the reset, the on-chip oscillator will be
used by default.The external oscillator can be selected via software. In addition, the PLL
provides a fail-safe logic to perform oscillator run and loss-of-lock detection. This allows
emergency routines to be executed for system recovery or to perform system shut down.
Figure 23
Data Sheet
OSC
fosc
Clock Generation Unit
CGU Block Diagram
P:1
OSCDISC
f p
f n
osc fail
detect
detect
core
lock
PLL
NDIV
N:1
57
fvco
VCOBYP
1
0
K:1
Functional Description
fsys
V1.2, 2007-10
OSCR
LOCK
XC866