Maxim Integrated MAXQ610 - Manual (Page 26)

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MAXQ610 User’s Guide
2.7 Clock Generation
All functional modules in the MAXQ610 are synchronized to a single system clock with the exception of the wakeup
timer . The internal clock circuitry generates the system clock from one of two possible sources:
• Internal oscillator, using an external crystal or resonator
• External clock signal
The external clock and crystal are mutually exclusive since they are input through the same clock pin . Each time code
execution must start or restart (as can be the case when exiting stop mode) using the external clock source, the fol-
lowing sequence occurs:
• Reset the crystal warmup counter.
• Allow the required warmup delay: 8192 external clock cycles if exiting from stop mode.
• Code execution starts after the crystal warmup sequence.
Figure 2-9. MAXQ610 Clock Sources
GLITCH-FREE
MUX
DIV 1 DIV 2 DIV 4 DIV 8 PMM
CLOCK
DIVIDER
SELECTOR
DEFAULT
WATCHDOG
TIMER
RESET DOG
RWT
RESET
POWER-ON
RESET
STOP
STOP
POWER-ON
RESET
SWB
INTERRUPT/SERIAL PORT
RESET
STOP
WATCHDOG RESET
CLOCK
GENERATION
SYSTEM CLOCK
ENABLE
WATCHDOG INTERRUPT
HF
CRYSTAL
8kHz
RING
WAKE-UP TIMER
CRYSTAL KILL
XDOG
STARTUP
TIMER
CLK INPUT
RESET
XDOG DONE
MAXQ610