topic Re: S12ZVM12 Memory model and pointer size in S12 / MagniV Microcontrollers

S12ZVM12 Memory model and pointer size

ameykhatavkar — Wed, 17 Feb 2016 05:26:43 GMT

Hi Team,

As I understand, the memory model are defined to set the accesses to global non-constant data,

i.e. small model has 14 bit access, medium model has 18 bit and large model has 24bit access.

According these memory model, the size of pointer to non-constant data (int *) must be like,

Small = 2 byte(14bit), Medium= 3byte(18bit) , Large = 3byte (24bit).

But I observed that this is the not right scenario considering the small memory model. In the case of small memory model it is also of size 3byte.

This I confirmed as follows -

Created the project with Small memory model in Code warrior 10.6.4

int data = 0xff;

int *ptr1;

int sizePtr;

void main(void)

{

ptr1 = &data;

sizePtr = sizeof(ptr1);

for(;;) {

}

Here the size of pointer 'ptr1' getting in sizePtr as 3.

Also I have confirmed the size of memory allocated for the pointer ptr1by looking into map file and here also it taking as 3 byte.

Please clarify/correct me. Is it a wrong scenario? or compiler is not taking care properly.

Regards,

Amey

Re: S12ZVM12 Memory model and pointer size

ameykhatavkar — Mon, 22 Feb 2016 08:20:07 GMT

Hi,

Anybody have seen this?

please reply. I am waiting

Regards,

Amey

Re: S12ZVM12 Memory model and pointer size

trytohelp — Mon, 22 Feb 2016 15:31:48 GMT

Hi Amey,

It seems you refer to the pointer description at MCU_S12Z_Compiler.pdf compiler page 163:

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

Following the rule for the code:

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

int data = 0xff;

int *ptr1;

int sizePtr;

void main(void) {

EnableInterrupts;

/* include your code here */

ptr1 = &data;

sizePtr = sizeof(ptr1);

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

Sizeptr returns the value 3.

I've reproduced the problem on my side.

I need to investigate it and keep you informed

Have a great day,
Pascal
NXP Technical Support

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Re: S12ZVM12 Memory model and pointer size

trytohelp — Tue, 23 Feb 2016 08:44:42 GMT

Hi Amey,

I've contacted the compiler team and got more information.

The size of the pointer within the program (i.e. sizeof(<pointer type>) is always 24-bit (i.e. 3-byte).

The table below (from the compiler manual) refers to the size of the addresses that are stored in the pointer types:

for small and medium memory models the addresses used for non-constant global data (RAM) are smaller (due to the encoding of the instructions using RAM addresses, resulting in smaller encoding size, if the application data fits in 14 / 18 – bits RAM addresses)
the other types of data (constant data or code) are placed in ROM, which require 24-bit addresses

Have a great day,
Pascal
NXP Technical Support