mc68hc908kx8 Freescale Semiconductor, Inc, mc68hc908kx8 Datasheet - Page 73

• Manufacturer Part Number: mc68hc908kx8
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

7.3.4 Clock Monitor Circuit
The ICG contains a clock monitor circuit which, when enabled, will continuously monitor both the external
clock (ECLK) and the internal clock (ICLK) to determine if either clock source has been corrupted. The
clock monitor circuit, shown in
7.3.4.1 Clock Monitor Reference Generator
The clock monitor uses a reference based on one clock source to monitor the other clock source. The
clock monitor reference generator generates the external reference clock (EREF) based on the external
clock (ECLK) and the internal reference clock (IREF) based on the internal clock (ICLK). To simplify the
circuit, the low frequency base clock (IBASE) is used in place of ICLK because it always operates at or
Freescale Semiconductor
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Clock monitor reference generator
Internal clock activity detector
External clock activity detector
EXTSLOW
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
EXTXTALEN
NAME
ECGEN
NAME
CMON
FICGS
ICGEN
IBASE
ECLK
Figure 7-4. Clock Monitor Block Diagram
Figure
CONFIGURATION (OR MOR) REGISTER BIT
TOP LEVEL SIGNAL
7-4, contains these blocks:
FICGS
IBASE
ICGEN
EREF
IBASE
ICGON
EXTXTALEN
EXTSLOW
ECGS
ECLK
ECGEN
IREF
ECGEN
ECLK
CMON
CMON
ESTBCLK
DETECTOR
DETECTOR
ACTIVITY
ACTIVITY
ICLK
ECLK
GENERATOR
REFERENCE
ESTBCLK
EREF
ECGS
EOFF
IREF
IOFF
ICGS
NAME
NAME
MODULE SIGNAL
REGISTER BIT
ECGS
ICGS
EOFF
IOFF
Functional Description
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