S9S08AW16A FREESCALE [Freescale Semiconductor, Inc], S9S08AW16A Datasheet - Page 133

• Manufacturer Part Number: S9S08AW16A
• Description: HCS08 Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

1
8.3.1
Freescale Semiconductor
This bit can be written only once after reset. Additional writes are ignored.
OSCSTEN
Reset
RANGE
LOCD
REFS
CLKS
Field
HGO
4:3
7
6
5
2
1
W
R
ICG Control Register 1 (ICGC1)
HGO
High Gain Oscillator Select — The HGO bit is used to select between low power operation and high gain
operation for improved noise immunity. This bit is write-once after reset.
0 Oscillator configured for low power operation.
1 Oscillator configured for high gain operation.
Frequency Range Select — The RANGE bit controls the oscillator, reference divider, and FLL loop prescaler
multiplication factor (P). It selects one of two reference frequency ranges for the ICG. The RANGE bit is
write-once after a reset. The RANGE bit only has an effect in FLL engaged external and FLL bypassed external
modes.
0 Oscillator configured for low frequency range. FLL loop prescale factor P is 64.
1 Oscillator configured for high frequency range. FLL loop prescale factor P is 1.
External Reference Select — The REFS bit controls the external reference clock source for ICGERCLK. The
REFS bit is write-once after a reset.
0 External clock requested.
1 Oscillator using crystal or resonator requested.
Clock Mode Select — The CLKS bits control the clock mode as described below. If FLL bypassed external is
requested, it will not be selected until ERCS = 1. If the ICG enters off mode, the CLKS bits will remain unchanged.
Writes to the CLKS bits will not take effect if a previous write is not complete.
00 Self-clocked
01 FLL engaged, internal reference
10 FLL bypassed, external reference
11 FLL engaged, external reference
The CLKS bits are writable at any time, unless the first write after a reset was CLKS = 0X, the CLKS bits cannot
be written to 1X until after the next reset (because the EXTAL pin was not reserved).
Enable Oscillator in Off Mode — The OSCSTEN bit controls whether or not the oscillator circuit remains
enabled when the ICG enters off mode. This bit has no effect if HGO = 1 and RANGE = 1.
0 Oscillator disabled when ICG is in off mode unless ENABLE is high, CLKS = 10, and REFST = 1.
1 Oscillator enabled when ICG is in off mode, CLKS = 1X and REFST = 1.
Loss of Clock Disable
0 Loss of clock detection enabled.
1 Loss of clock detection disabled.
0
7
1
= Unimplemented or Reserved
RANGE
1
6
Table 8-1. ICGC1 Register Field Descriptions
Figure 8-6. ICG Control Register 1 (ICGC1)
MC9S08AC16 Series Data Sheet, Rev. 8
REFS
0
5
0
4
Description
CLKS
3
0
OSCSTEN
1
2
Internal Clock Generator (S08ICGV4)
LOCD
0
1
0
0
0
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