Chapter 7 S12 Clock, Reset and Power Management Unit (S12CPMU_UHV_V5)
S12ZVHY/S12ZVHL Family Reference Manual, Rev. 1.05
Freescale Semiconductor
285
7.4.6
System Clock Configurations
7.4.6.1
PLL Engaged Internal Mode (PEI)
This mode is the default mode after System Reset or Power-On Reset.
The Bus Clock is based on the PLLCLK, the reference clock for the PLL is internally generated (IRC1M).
The PLL is configured to 50 MHz VCOCLK with POSTDIV set to 0x03. If locked (LOCK=1) this results
in a PLLCLK of 12.5 MHz and a Bus Clock of 6.25 MHz. The PLL can be re-configured to other bus
frequencies.
The clock sources for COP and RTI can be based on the internal reference clock generator (IRC1M) or the
RC-Oscillator (ACLK).
7.4.6.2
PLL Engaged External Mode (PEE)
In this mode, the Bus Clock is based on the PLLCLK as well (like PEI). The reference clock for the PLL
is based on the external oscillator.
The clock sources for COP and RTI can be based on the internal reference clock generator or on the
external oscillator clock or the RC-Oscillator (ACLK).
This mode can be entered from default mode PEI by performing the following steps:
1. Configure the PLL for desired bus frequency.
2. Enable the external Oscillator (OSCE bit).
3. Wait for oscillator to start-up and the PLL being locked (LOCK = 1) and (UPOSC =1).
4. Clear all flags in the CPMUIFLG register to be able to detect any future status bit change.
5. Optionally status interrupts can be enabled (CPMUINT register).
Loosing PLL lock status (LOCK=0) means loosing the oscillator status information as well (UPOSC=0).
The impact of loosing the oscillator status (UPOSC=0) in PEE mode is as follows:
•
The PLLCLK is derived from the VCO clock (with its actual frequency) divided by four until the
PLL locks again.
Application software needs to be prepared to deal with the impact of loosing the oscillator status at any
time.
Содержание MC9S12ZVHL32
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Страница 686: ...Chapter 20 ECC Generation module SRAM_ECCV1 S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 686 Freescale Semiconductor...
Страница 752: ...Chapter 22 Supply Voltage Sensor BATSV2 S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 752 Freescale Semiconductor...
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Страница 788: ...Appendix A MCU Electrical Specifications S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 788 Freescale Semiconductor...
Страница 794: ...Appendix B ADC Electricals S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 794 Freescale Semiconductor...
Страница 798: ...Appendix D IRC Electrical Specifications S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 798 Freescale Semiconductor...
Страница 802: ...Appendix F MSCAN Electrical Specifications S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 802 Freescale Semiconductor...
Страница 806: ...Appendix G NVM Electrical Parameters S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 806 Freescale Semiconductor...
Страница 810: ...Appendix H BATS Electrical Specifications S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 810 Freescale Semiconductor...
Страница 816: ...Appendix K OSC32K Electrical Specifications S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 816 Freescale Semiconductor...
Страница 822: ...Appendix L SPI Electrical Specifications S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 822 Freescale Semiconductor...
Страница 826: ...Appendix M LINPHY Electrical Specifications S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 826 Freescale Semiconductor...
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