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...?T and ...?A

Dave Sudolcan

The following comment is on a website for the pC/OS RTOS kernel (http://www.embedded-os.de/)


The port of the pC/OS Kernel on AT91SAM7Sxx is now finished.
As Toolchain the IAR Embedded Workbench was used. Sorry to Keil, with "...?T" and "...?A" it's not really possible to create a good port for ARM and Thumb mode.


If anyone knows what this means, will you please explain it?

Thanks.

Parents Reply Children
  • 0 in reply to Frank Goetze

    I need help....
    The following code fragment is the start of Task1() without the two memory-manager calls (commented). If I step over/in " b 0x001010d8" the processor jumps to the DAbt_Handler at address 0x00000010.
    Whats wrong with this part ???

      B530    push    {r4-r5,lr}
  2400    mov     r4,#0x00
  F000    bl      AppTickInit(0x00101290) - Part #1
  F8DE    bl      AppTickInit(0x00101290) - Part #2
  E000    b       0x001010d8        -               *** -> DAbt_Handler(0x00000010)
  3401    add     r4,#0x01           |  <-
  1C20    add     r0,r4,#0         <-     |
  4911    ldr     r1,[pc,#0x0044]         |
  4288    cmp     r0,r1                   |
  D3FA    bcc     0x001010d6          ----
  ...

  • 0 in reply to Frank Goetze

    Frank,

    Your code snipped shows -

      ...
  F000    bl      AppTickInit(0x00101290) - Part #1
  F8DE    bl      AppTickInit(0x00101290) - Part #2
  ...

    The opcodes indicate that the code is runing in thumb mode. But the target of the 'BL' shows 0x00101290, this is Arm-mode (even address, thumb mode would be 0x00101291).
    In this case, you need an interwork-stub, that is code that changes from thumb- to arm-mode.

    Here is an example of how that looks like:

    //--- Thumb-mode:
 ...
 01000CCE  3001      ADD         R0,#0x1
 01000CD0  3102      ADD         R1,#0x2
 01000CD2  F7FF      BL          AppTickInit?T  ; T=0x1000C71  (1)
 01000CD4  FFCD      BL          AppTickInit?T  ; T=0x1000C71  (2)
 ...

//--- Thumb to Arm Interwork-Stub:
 01000C70          AppTickInit?T PROC THUMB
 01000C70  4778      BX          R15
 01000C72  46C0      NOP         ; MOV R8,R8
 01000C74          ENDP

//--- Arm Function:
 01000C74          AppTickInit?A:  ; FUNCTION START
  257: int ArmF (int n1, int n2) __arm {
 01000C74  E1A03001  MOV         R3,R1 ; n2
 01000C78  ---- Variable 'n2' assigned to Register 'R3' ----
 01000C78  E1A02000  MOV         R2,R0 ; n1
 01000C7C  ---- Variable 'n1' assigned to Register 'R2' ----
  258:   return (n1 * n2 + n1 * n2);
 01000C7C  E1A01003  MOV         R1,R3 ; n2
 01000C80  E1A00002  MOV         R0,R2 ; n1
 01000C84  E0000091  MUL         R0,R1,R0 ; n2
 01000C88  E0800000  ADD         R0,R0,R0
  259: }
 01000C8C  E12FFF1E  BX          R14
 01000C90            ; END 'AppTickInit?A'

    Peter

  • 0 in reply to Gp F

    thanks,

    but see the main.c - AppTickInit() is a C-function called from main(). I think, this is to handle by the compiler...
    Have the Keil-compiler optimizing problems with not direct called functions (see Task1..3) or problems with C-Thumb-code mixed with ASM-Thumb/ARM-code ?

    Frank

  • 0 in reply to Frank Götze

    ... Sorry !

    see the main.c - AppTickInit() is a C-function called from C-function Task1().
    But the problem is still the same...

  • 0 in reply to Frank Götze

    ... more tests using the simulator and the board...
    Following test was running on the board:

    * If I set a breakpoint at 

    bl      AppTickInit(0x00101290) - Part #1
    register r4 is not zero in the register-window???
    * if I set a breakpoint at 
    push    {r4-r5,lr}
    and step forward, the register r4 will initialised with zero.

    What's wrong ???

    If I add a secound variable that will located in register r5 and the init is in front of r4, like 
      B530    push    {r4-r5,lr}
  2500    mov     r5,#0x00
  2400    mov     r4,#0x00
    and I break on init of r4 or later, then r5 is not zero in the register-window ???

  • 0 in reply to Frank Götze

    The CARM compiler handles all the interworking automatically. As usual with software, there is always the chance to get into some 'notch'. You should provide a boiled down example since the code fragments simply don't give enough details. Your most recent post looks like a stack overrun/underrun problem.

    Peter

  • 0 in reply to Gp F

    You can download the hole code of the pC/OS RTOS kernel from http://www.embedded-os.de/index.html?pcos.htm