[参考译文] TMS320F28.0039万C：FreeRTOS交换上下文

StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
{
  volatile uint16_t i;

  base = 0;

  pxTopOfStack[base++]  = 0x0080;  // ST0. PSM = 0(No shift)
  pxTopOfStack[base++]  = 0x0000;  // T
  pxTopOfStack[base++]  = 0x0000;  // AL
  pxTopOfStack[base++]  = 0x0000;  // AH
  pxTopOfStack[base++]  = 0xFFFF;  // PL
  pxTopOfStack[base++]  = 0xFFFF;  // PH
  pxTopOfStack[base++]  = 0xFFFF;  // AR0
  pxTopOfStack[base++]  = 0xFFFF;  // AR1
  pxTopOfStack[base++]  = 0x8A08;  // ST1
  pxTopOfStack[base++]  = 0x0000;  // DP
  pxTopOfStack[base++] = 0x2000 | IER;    // IER at the moment of creating tasks, make sure INT14 is enabled
  pxTopOfStack[base++] = 0x0000;  // DBGSTAT
  pxTopOfStack[base++] = ((uint32_t)pxCode) & 0xFFFFU;       // PCL
  pxTopOfStack[base++] = ((uint32_t)pxCode >> 16) & 0x00FFU; // PCH
  pxTopOfStack[base++] = 0xAAAA;  // Alignment
  pxTopOfStack[base++] = 0xBBBB;  // Alignment

  // Fill the rest of the registers with dummy values.
  for(i = 0; i < (2 * AUX_REGISTERS_TO_SAVE); i++)
  {
    uint16_t low  = 0xAAAA;
    uint16_t high = 0xAAAA;

    if(i == (2 * XAR4_REGISTER_POSITION))
    {
      low  = ((uint32_t)pvParameters) & 0xAAAAU;
      high = ((uint32_t)pvParameters >> 16) & 0xAAAAU;
    }

#if defined(__TMS320C28XX_FPU32__)
    if(i == (2 * STF_REGISTER_POSITION))
    {
      uint32_t stf = getSTF();

      low  = stf & 0xAAAAU;
      high = (stf >> 16) & 0xAAAAU;
    }
#endif

    pxTopOfStack[base + i] = low;
    i++;
    pxTopOfStack[base + i] = high;
  }

  base += i;

  // Reserve place for ST1 which will be used in context switch
  // to set correct SPA bit ASAP.
  pxTopOfStack[base++] = 0x8A18;  // ST1 with SPA bit set
  pxTopOfStack[base++] = 0x0000;  // DP
  pxTopOfStack[base++] = 0x0000;  // placeholder for 32 bit ulCriticalVars
  pxTopOfStack[base++] = 0x0000;

  // Return a pointer to the top of the stack we have generated so this can
  // be stored in the task control block for the task.
  return pxTopOfStack + base;
}

portRESTORE_FIRST_CONTEXT
; Restore stack pointer from new task control block.
  MOVL    XAR0, #pxCurrentTCB
  MOVL    XAR0, *XAR0
  MOVL    XAR0, *XAR0
  MOV     @SP, AR0

; Restore XAR4 and RPC from saved task stack.
; and return to main task function.
; SP should be set to stack start plus 2 before LRETR.
  SUBB   SP, #XAR4_DELTA
  POP    XAR4
  SUBB   SP, #RPC_DELTA
  POP    RPC
  SUBB   SP, #SP_TOP_DELTA
  CLRC    INTM, DBGM    ; renable global interrupts
  LRETR
  .endasmfunc

And this is the part of Restore Context inside the ISR
RESTORE_CONTEXT:
  POP     DP:ST1
  .if .TMS320C2800_FPU32 = 1
  MOV32   R7H, *--SP
  MOV32   R6H, *--SP
  MOV32   R5H, *--SP
  MOV32   R4H, *--SP
  MOV32   R3H, *--SP
  MOV32   R2H, *--SP
  MOV32   R1H, *--SP
  MOV32   R0H, *--SP
  MOV32   STF, *--SP
  POP     RB
  .endif
  POP     XAR7
  POP     XAR6
  POP     XAR5
  POP     XAR4
  POP     XAR3
  POP     XAR2
  POP     XT
  POP     RPC
  POP     AR1H:AR0H
  NASP
  IRET