Math code in RAM issue - EWL library in RAM

masettic — Wed, 23 Apr 2014 08:42:04 GMT

Hi,

I am currently developing a project with CW 10.1 on a K60 MCU.

I have successfully managed to place my code in RAM but I have encountered some issues while performing math operations which call for library functions. Here follows some sample code:

main.c:

#include <stdio.h>

#include <math.h>

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

#pragma define_section text ".text" ".text" ".text" far_abs RX

#pragma define_section RAMCode ".RAMCode" ".RAMCode" ".RAMCode" far_abs RX

__declspec(RAMCode) int myRAMfunction(int cnt);

int main(void)

{

int counter = 0;

for(;;) {

counter++;

counter = myRAMfunction(counter);

}

return 0;

}

__declspec(RAMCode) int myRAMfunction(int cnt)

{

cnt = __aeabi_idiv(cnt,3);

cnt = cnt /3;

return cnt;

}

Linker command file:

MEMORY {

m_interrupts (RX) : ORIGIN = 0x00000000, LENGTH = 0x000001E0

m_text (RX) : ORIGIN = 0x00000800, LENGTH = 0x00080000-0x00000800

m_data (RW) : ORIGIN = 0x1FFF0000, LENGTH = 0x00010000

m_RAMexec (RX) : ORIGIN = 0x20000000, LENGTH = 0x00001000

m_cfmprotrom (RX) : ORIGIN = 0x00000400, LENGTH = 0x00000010

}

......

.RAMexec:

{

. = ALIGN (0x8);

* (.RAMCode)

. = ALIGN (0x8);

} > m_RAMexec

....

The first #pragma sets .text section as far_abs and allows to call flash stored functions, both user defined and (most) library ones, in myRAMfunction.

As I try to perform, for example, a division operation, the MCU generates an exception.

However, the code runs smoothly if I directly call the library function __aeabi_idiv which seems to be the function the compiler calls while performing a division.

Looking at the disassembly while debugging sheds a bit of light:

myRAMfunction:

20000000: push {r4,lr}

20000002: cpy r4,r0

27 cnt = __aeabi_idiv(cnt,3);

20000004: ldr r2,[pc,#0x1c]

20000008: cpy r0,r4

2000000a: movs r1,#3

2000000c: blx r2

2000000e: cpy r4,r0

28 cnt = cnt /3;

20000010: cpy r0,r4

20000012: movs r1,#3

20000014: bl $Ven$lb$$__aeabi_idiv._s32_div_f.o (0x20000028); 0x20000028

20000018: cpy r4,r0

29 return cnt;

2000001a: cpy r0,r4

30 }

2000001c: ldm sp!,{r4,lr}

20000020: bx lr

20000022: nop

20000024: lsrs r5,r5,#16

20000026: movs r0,r0

20000028: bx pc

It seems that the compiler carries out the second division with a branch link to $Ven$lb$$__aeabi_idiv._s32_div_f.o, which unfortunately points to nowhere (0x20000028), while the explicit call to __aeabi_idiv works fine, moving the PC back to the flash section where the integer division code is stored.

1. Does anybody know how to solve this issue?

2. Is there a smooth way to load the math EWL libraries in RAM?

Re: Math code in RAM issue - EWL library in RAM

Jorge_Gonzalez — Fri, 25 Apr 2014 18:22:52 GMT

Hello Cesare:

Is it possible for you to share your project? I would like to reproduce this issue from my side and see if I can find the problem. Also please tell us the exact part number you have.

Regards!

Jorge Gonzalez

Re: Math code in RAM issue - EWL library in RAM

masettic — Tue, 29 Apr 2014 07:25:36 GMT

Hello,

found an answer to both questions:

1. The issue related to the assembly branch link seems to originate from a CW 10.1 Linker bug. Simply substituting the linker .exe with a new one (version 10.5) solves the problem: now at address 0x20000028, after the bl, there is another branch to the flash stored division code. Everything now works fine.

2. I have found in another post Re: Calling all LCF Experts... the correct sintax to move a whole EWL library to RAM.

Best regards,

Cesare

topic Math code in RAM issue - EWL library in RAM in Kinetis Microcontrollers

Math code in RAM issue - EWL library in RAM

Re: Math code in RAM issue - EWL library in RAM

Re: Math code in RAM issue - EWL library in RAM