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Chapter 1 Device Overview MC9S12ZVM-Family
MC9S12ZVM Family Reference Manual Rev. 1.3
Freescale Semiconductor
23
1.4.3
Clocks, Reset & Power Management Unit (CPMU)
•
Real time interrupt (RTI)
•
Clock monitor, supervising the correct function of the oscillator (CM)
•
Computer operating properly (COP) watchdog
— Configurable as window COP for enhanced failure detection
— Can be initialized out of reset using option bits located in flash memory
•
System reset generation
•
Autonomous periodic interrupt (API) (combination with cyclic, watchdog)
•
Low Power Operation
— RUN mode is the main full performance operating mode with the entire device clocked.
— WAIT mode when the internal CPU clock is switched off, so the CPU does not execute
instructions.
— Pseudo STOP - system clocks are stopped but the oscillator the RTI, the COP, and API modules
can be enabled
— STOP - the oscillator is stopped in this mode, all clocks are switched off and all counters and
dividers remain frozen, with the exception of the COP and API which can optionally run from
ACLK.
1.4.3.1
Internal Phase-Locked Loop (IPLL)
•
Phase-locked-loop clock frequency multiplier
— No external components required
— Reference divider and multiplier allow large variety of clock rates
— Automatic bandwidth control mode for low-jitter operation
— Automatic frequency lock detector
— Configurable option to spread spectrum for reduced EMC radiation (frequency modulation)
— Reference clock sources:
– Internal 1 MHz RC oscillator (IRC)
– External 4-20 MHz crystal oscillator/resonator
1.4.3.2
Internal RC Oscillator (IRC)
•
Trimmable internal 1MHz reference clock.
— Trimmed accuracy over -40
°
C to 150
°
C junction temperature range:
±
1.3%max.
1.4.4
Main External Oscillator (XOSCLCP)
•
Amplitude controlled Pierce oscillator using 4 MHz to 20 MHz crystal
— Current gain control on amplitude output
— Signal with low harmonic distortion