Internal Clock Generator (S08ICGV2)
MC9S08GB60A Data Sheet, Rev. 2
126
Freescale Semiconductor
7.5.3
ICG Status Register 1 (
ICGS1)
76
54
321
0
R
CLKST
REFST
LOLS
LOCK
LOCS
ERCS
ICGIF
W
1
Reset
000
00
000
= Unimplemented or Reserved
Figure 7-14. ICG Status Register 1 (ICGS1)
Table 7-8. ICGS1 Field Descriptions
Field
Description
7:6
CLKST
Clock Mode Status — The CLKST bits indicate the current clock mode. The CLKST bits don’t update
immediately after a write to the CLKS bits due to internal synchronization between clock domains.
00 Self-clocked
01 FLL engaged, internal reference
10 FLL bypassed, external reference
11 FLL engaged, external reference
5
REFST
Reference Clock Status — The REFST bit indicates which clock reference is currently selected by the
Reference Select circuit.
0
External Clock selected.
1
Crystal/Resonator selected.
4
LOLS
FLL Loss of Lock Status — The LOLS bit is an indication of FLL-lock status. If LOLS is set, it remains set until
cleared by clearing the ICGIF flag or an MCU reset.
0
FLL has not unexpectedly lost lock since LOLS was last cleared.
1
FLL has unexpectedly lost lock since LOLS was last cleared, LOLRE determines action taken.
3
LOCK
FLL Lock Status — The LOCK bit indicates whether the FLL has acquired lock. The LOCK bit is cleared in off,
self-clocked, and FLL bypassed modes.
0
FLL is currently unlocked.
1
FLL is currently locked.
2
LOCS
Loss Of Clock Status — The LOCS bit is an indication of ICG loss-of-clock status. If LOCS is set, it remains set
until cleared by clearing the ICGIF flag or an MCU reset.
0
ICG has not lost clock since LOCS was last cleared.
1
ICG has lost clock since LOCS was last cleared, LOCRE determines action taken.
1
ERCS
External Reference Clock Status — The ERCS bit is an indication of whether or not the external reference clock
(ICGERCLK) meets the minimum frequency requirement.
0
External reference clock is not stable, frequency requirement is not met.
1
External reference clock is stable, frequency requirement is met.
0
ICGIF
ICG Interrupt Flag — The ICGIF read/write flag is set when an ICG interrupt request is pending. It is cleared by
a reset or by reading the ICG status register when ICGIF is set and then writing a 1 to ICGIF. If another ICG
interrupt occurs before the clearing sequence is complete, the sequence is reset so ICGIF would remain set after
the clear sequence was completed for the earlier interrupt. Writing a 0 to ICGIF has no effect.
0
No ICG interrupt request is pending.
1
An ICG interrupt request is pending.