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Chapter 8 S12 Clock, Reset and Power Management Unit (S12CPMU_UHV_V6)
MC9S12ZVM Family Reference Manual Rev. 1.3
Freescale Semiconductor
305
8.7
Initialization/Application Information
8.7.1
General Initialization Information
Usually applications run in MCU Normal Mode
.
It is recommended to write the CPMUCOP register in any case from the application program initialization
routine after reset no matter if the COP is used in the application or not, even if a configuration is loaded
via the flash memory after reset
.
By doing a “controlled” write access in MCU Normal Mode (with the
right value for the application) the write once for the COP configuration bits (WCOP,CR[2:0]) takes place
which protects these bits from further accidental change
.
In case of a program sequencing issue (code
runaway) the COP configuration can not be accidentally modified anymore
.
8.7.2
Application information for COP and API usage
In many applications the COP is used to check that the program is running and sequencing properly. Often
the COP is kept running during Stop Mode and periodic wake-up events are needed to service the COP on
time and maybe to check the system status
.
For such an application it is recommended to use the ACLK as clock source for both COP and API. This
guarantees lowest possible IDD current during Stop Mode
.
Additionally it eases software implementation
using the same clock source for both, COP and API
.
The Interrupt Service Routine (ISR) of the Autonomous Periodic Interrupt API should contain the write
instruction to the CPMUARMCOP register. The value (byte) written is derived from the “main routine”
(alternating sequence of $55 and $AA) of the application software
.
Using this method, then in the case of a runtime or program sequencing issue the application “main
routine” is not executed properly anymore and the alternating values are not provided properly. Hence the
COP is written at the correct time (due to independent API interrupt request) but the wrong value is written
(alternating sequence of $55 and $AA is no longer maintained) which causes a COP reset
.
If the COP is stopped during any Stop Mode it is recommended to service the COP shortly before Stop
Mode is entered.
8.7.3
Application Information for PLL and Oscillator Startup
The following C-code example shows a recommended way of setting up the system clock system using
the PLL and Oscillator:
/* Procedure proposed by to setup PLL and Oscillator */
/* example for OSC = 4 MHz and Bus Clock = 25MHz, That is VCOCLK = 50MHz */
/* Initialize */
/* PLL Clock = 50 MHz, divide by one */
CPMUPOSTDIV = 0x00;
/* Generally: Whenever changing PLL reference clock (REFCLK) frequency to a higher value */
Содержание MC9S12ZVM series
Страница 116: ...Chapter 2 Port Integration Module S12ZVMPIMV1 MC9S12ZVM Family Reference Manual Rev 1 3 116 Freescale Semiconductor ...
Страница 242: ...Chapter 7 ECC Generation Module SRAM_ECCV1 MC9S12ZVM Family Reference Manual Rev 1 3 242 Freescale Semiconductor ...
Страница 384: ...Chapter 10 Supply Voltage Sensor BATSV3 MC9S12ZVM Family Reference Manual Rev 1 3 384 Freescale Semiconductor ...
Страница 484: ...Chapter 13 Programmable Trigger Unit PTUV2 MC9S12ZVM Family Reference Manual Rev 1 3 484 Freescale Semiconductor ...
Страница 662: ...Chapter 17 Gate Drive Unit GDUV4 MC9S12ZVM Family Reference Manual Rev 1 3 662 Freescale Semiconductor ...
Страница 684: ...Chapter 18 LIN Physical Layer S12LINPHYV2 MC9S12ZVM Family Reference Manual Rev 1 3 684 Freescale Semiconductor ...
Страница 740: ...Chapter 19 128 KB Flash Module S12ZFTMRZ128K512V2 MC9S12ZVM Family Reference Manual Rev 1 3 740 Freescale Semiconductor ...
Страница 756: ...Appendix A MCU Electrical Specifications MC9S12ZVM Family Reference Manual Rev 1 3 756 Freescale Semiconductor ...
Страница 772: ...Appendix D LINPHY Electrical Specifications MC9S12ZVM Family Reference Manual Rev 1 3 772 Freescale Semiconductor ...
Страница 776: ...Appendix E GDU Electrical Specifications MC9S12ZVM Family Reference Manual Rev 1 3 776 Freescale Semiconductor ...
Страница 788: ...Appendix I MSCAN Electrical Specifications MC9S12ZVM Family Reference Manual Rev 1 3 788 Freescale Semiconductor ...
Страница 790: ...Appendix J Package Information MC9S12ZVM Family Reference Manual Rev 1 3 790 Freescale Semiconductor ...