MCU Internal Clock Generator (ICG)
MC1321x Reference Manual, Rev. 1.6
14-14
Freescale Semiconductor
Bit 6
RANGE
0
Configures oscillator for low-frequency range; FLL prescale factor is 64
Bit 5
REFS
1
Oscillator using crystal or resonator is requested
Bits 4:3 CLKS
11
FLL engaged, external reference clock mode
Bit 2
OSCSTEN 0
Oscillator disabled in stop modes
Bit 1
LOCD
0
Loss-of-clock detection enabled
Bit 0
0
Unimplemented or reserved, always reads zero
ICGC2 = $00 (%00000000)
Bit 7
LOLRE
0
Generates an interrupt request on loss of lock
Bits 6:4 MFD
000
Sets the MFD multiplication factor to 4
Bit 3
LOCRE
0
Generates an interrupt request on loss of clock
Bits 2:0 RFD
000
Sets the RFD division factor to
÷
1
ICGS1 = $xx
This is read only except for clearing interrupt flag
ICGS2 = $xx
This is read only; should read DCOS = 1 before performing any time critical tasks
ICGFLTLU/L = $xx
Only needed in Self-clocked Mode; FLT will be adjusted by loop to give 8.38 MHz DCO clock
Bits 15:12 unused
0000
Bits 11:0 FLT
No need for user initialization
ICGTRM = $xx
Bits 7:0
TRIM
Only need to write when trimming internal oscillator; not used when external
crystal is clock source
shows flow charts for three conditions requiring ICG initialization.
Figure 14-6. ICG Initialization for FEE in Example #1
RECOVERY FROM
CONTINUE
RECOVERY FROM STOP3
CHECK
LOCK = 1?
NO
YES
FLL LOCK STATUS.
INITIALIZE ICG
ICG1 = $38
ICG2 = $00
RECOVERY FROM STOP3
OSCSTEN = 1
OSCSTEN = 0
CONTINUE
CHECK
LOCK = 1?
NO
YES
FLL LOCK STATUS.
CONTINUE
CHECK
LOCK = 1?
NO
YES
FLL LOCK STATUS.
NOTE: THIS WILL REQUIRE THE OSCILLATOR TO START AND
STABILIZE. ACTUAL TIME IS DEPENDENT ON CRYSTAL /RESONATOR
AND EXTERNAL CIRCUITRY.
QUICK RECOVERY FROM STOP
MINIMUM CURRENT DRAW IN STOP
RESET, STIO1, STOP2
Содержание freescale semiconductor MC13211
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