topic Re: Problem with S12ZVC startup code in CodeWarrior Development Tools

Problem with S12ZVC startup code

amit_dhand — Tue, 01 Sep 2015 07:31:10 GMT

Hello,

I have a created a short code to initialise MCU clock before going to _Startup code.

Here is the code.

#include <hidef.h> /* for EnableInterrupts macro */

#include "derivative.h" /* include peripheral declarations */

#include <starts12z.h>

void PLL_init();

void interrupt VectorNumber_Vreset Vreset_ISR();

void interrupt VectorNumber_Vreset Vreset_ISR()

{

PLL_init();

}

void main(void)

{

EnableInterrupts;

/* include your code here */

for(;;) {

__RESET_WATCHDOG(); /* feeds the dog */

} /* loop forever */

/* please make sure that you never leave main */

}

void PLL_init()

{

CPMUCLKS_PLLSEL = 1; //FBUS = FPLL/2. FBUS = 32MHz,

CPMUREFDIV_REFFRQ = 1; //Reference clock between 2MHZ and 6MHZ.

CPMUREFDIV_REFDIV = 0x1; //FREF=8/(1+1) = 4MHZ

CPMUSYNR_VCOFRQ = 0x1; //FVCO is between 48MHZ and 80MHZ

CPMUSYNR_SYNDIV = 0x7; //FVCO = 2xFREFx(SYNDIV+1) = FVCO = 2x4x(7+1) = 64MHZ

CPMUPOSTDIV_POSTDIV = 0x0; //FPLL = FVCO/(POSTDIV+1). FPLL = 64MHZ/(0+1) FPLL = 64MHz

CPMUOSC_OSCE = 1; //External oscillator enable. 8MHZ. FREF=FOSC/(REFDIV+1)

while(!CPMUIFLG_LOCK){} // Wait for LOCK.

CPMUIFLG = 0xFF; // clear CMPMU int flags - not needed but good practice

__asm(jmp _Startup); /* Jump to C startup code */

}

I commented this part of code from LCF file

VECTOR 0 _Startup /* reset vector: this is the default entry point for a C/C++ application. */

But the issue is now every time I debug the code with the setting as program entry point, it always jump into the startup code. It never comes to this function PLL_init.

I would like to know how S12ZVC microcontroller is configured for the program startup.

Thank you,

Amit Dhand

Re: Problem with S12ZVC startup code

trytohelp — Tue, 01 Sep 2015 09:00:05 GMT

Hi Amit,

I've created a short example based on S12ZVML128.

For the debug option I've selected Stop at entry function.

When I launch the debug session the application is loaded and point to void _Startup(void) function.

Now I added your code and commented the VECTOR 0 _Startup in prm file.

When I launch the Debugger, the application is loaded and point to the void _Startup(void) function too.

However if I click on reset, the application jump to the void interrupt VectorNumber_Vreset Vreset_ISR() function.

It should be the case on your side too.

Now the entry point is defined at _Startup function.

To change it you must define a new one and need to add in prm file (see add the end):

INIT Vreset_ISR

Now when I launch the debugger the application is loaded and point to:

void interrupt VectorNumber_Vreset Vreset_ISR()

Have a great day,
Pascal
Freescale Technical Support
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Re: Problem with S12ZVC startup code

amit_dhand — Tue, 01 Sep 2015 09:28:33 GMT

Thank you Pascal, This thing worked out.

Regards,

Amit Dhand

Re: Problem with S12ZVC startup code

amit_dhand — Tue, 01 Sep 2015 10:36:02 GMT

Hello Pascal,

Using keyword INIT in LCF file to start from the reset vector is fine. But I observed a weird thing that when the PLL_init function executes the first line of code it jumps to the undefined state.

Then to observe it more clearly I created a ProcessorExpert project for S12ZVC and generated the code.

I got the definition of ISR(Cpu_Interrupt) and I created a similar one for Vreset_ISR which called the _EntryPoint function

ISR(Cpu_Interrupt)

{

/*lint -save -e950 Disable MISRA rule (1.1) checking. */

asm(BGND);

/*lint -restore Enable MISRA rule (1.1) checking. */

}

ISR(Vreset_Interrupt)

{

_EntryPoint();

}

In LCF file

INIT Vreset_Interrupt

/* The entry point of the application. This function is generated into the CPU module. */

In vector.c vector table.

_VECTOR(Vreset_Interrupt)

/* 0x00FFFFFC ivVreset

used by PE */

When I debug and execute first instruction of the _EntryPoint function, it jumps into this Cpu_Interrupt function and stays there.

Can you help me out on this situation.

Regards,

Amit Dhand

Re: Problem with S12ZVC startup code

trytohelp — Tue, 01 Sep 2015 13:43:44 GMT

Hi Amit,

It's true than the example code created it's not working.

I didn't checked it as it was not the problem.

And you're right with PEx code too.

The problem is the same in both cases.

The Stack pointer is not initialized and I don't know exactly how is it defined by default.

Have a look to the cpu.c file.

Extract of void _EntryPoint(void)

{

...

/*lint -save -e950 Disable MISRA rule (1.1) checking. */

__asm(jmp _Startup); /* Jump to C startup code */

/*lint -restore Enable MISRA rule (1.1) checking. */

}

You can see the PEx code is not using c code to call the _Startup but the jmp assembly instruction.

The jmp is not saving the address function on stack.

It's important as the stack is not initialized in _EntryPoint but in _Startup only.

In the PEx example, if you change the code:

++++++++++++++

ISR(Vreset_Interrupt)

{

_EntryPoint();

}

++++++++++++++

by:

++++++++++++++

ISR(Vreset_Interrupt)

{

__asm(jmp _EntryPoint); /* Jump to _EntryPoint code */

}

++++++++++++++

BACK to your Example code.

Just change the code:

void interrupt VectorNumber_Vreset Vreset_ISR();

void interrupt VectorNumber_Vreset Vreset_ISR()

{

__asm(jmp PLL_init);

}

Now it's working.

Re: Problem with S12ZVC startup code

amit_dhand — Wed, 02 Sep 2015 08:14:19 GMT

Thank you Pascal, I also thought the stack initialisation could be an issue with you. But thanks for confirming it.

Regards,

Amit Dhand