MC9S08GB32 Motorola, MC9S08GB32 Datasheet - Page 103

• Manufacturer Part Number: MC9S08GB32
• Description: Microcontrollers
• Manufacturer: Motorola

7.3
This section provides a functional description of each of the five operating modes of the ICG. Also covered
are the loss of clock and loss of lock errors and requirements for entry into each mode. The ICG is very
flexible, and in some configurations, it is possible to exceed certain clock specifications. When using the
FLL, configure the ICG so that the frequency of ICGDCLK does not exceed its maximum value to ensure
proper MCU operation.
7.3.1
Normally when the CPU enters stop mode, the ICG will cease all clock activity and is in the off state.
However there are two cases to consider when clock activity continues while the CPU is in stop mode.
7.3.1.1
When the BDM is enabled, the ICG continues activity as originally programmed. This allows access to
memory and control registers via the BDC controller.
7.3.1.2
When the oscillator is enabled in stop mode (OSCSTEN = 1), the individual clock generators are enabled
but the clock feed to the rest of the MCU is turned off. This option is provided to avoid long oscillator
startup times if necessary, or to run the RTI from the oscillator during stop3.
Freescale Semiconductor
Functional Description
Off Mode (Off)
OSCSTEN Bit Set
BDM Active
Figure 7-5. External Frequency Reference Connection
EXTAL
MC9S08GB/GT Data Sheet, Rev. 2.3
CRYSTAL OR RESONATOR
C
1
ICG
V
R
SS
F
C
2
XTAL
R
S
Functional Description
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