MC9S08GT16A Datasheet, PDF (146/300 Pages) Freescale Semiconductor, Inc – Microcontrollers

Internal Clock Generator (S08ICGV4)
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
Figure 9-14 shows flow charts for three conditions requiring ICG initialization.
RESET
INITIALIZE ICG
ICGC1 = $38
ICGC2 = $00
CHECK
FLL LOCK STATUS. ^NO
LOCK = 1?
YES
QUICK RECOVERY FROM STOP
RECOVERY FROM STOP
OSCSTEN = 1
CHECK
FLL LOCK STATUS. ^NO
LOCK = 1?
YES
CONTINUE
MINIMUM CURRENT DRAW IN STOP
RECOVERY FROM STOP
OSCSTEN = 0
CHECK
FLL LOCK STATUS. ^NO
LOCK = 1?
YES
CONTINUE
CONTINUE
NOTE: THIS WILL REQUIRE THE OSCILLATOR TO START AND
STABILIZE. ACTUAL TIME IS DEPENDENT ON CRYSTAL /RESONATOR
AND EXTERNAL CIRCUITRY.
Figure 9-14. ICG Initialization for FEE in Example #1
MC9S08GT16A/GT8A Data Sheet, Rev. 1
146
Freescale Semiconductor