/*
*********************************************************************************************************
*                                      minOS 0.01v
*                                The Real-Time OS Kernel
*                                  All Rights Reserved
* File : OS_CPU.C
* 作者 : 21icbbs網友 LM7556 ,2004年7月   by : LM7556 , China , 2004-2004 
*
*********************************************************************************************************
*/

#define OS_CPU_GLOBALS
#include "OS_Includes.h"

#pragma interrupt_handler OSTickISR:8  //uses Timer0 for time ticks.

//;CPU specific definitions 
#define C51_CRYSTAL_FREQ   4000000ul
//;Determine the reload values for timer 0 this is automated by the next macro
#define T0_RELOAD  C51_CRYSTAL_FREQ / OS_TICKS_PER_SEC / 1024
#define T0_TCNT0 (256 - (T0_RELOAD & 0xff))
//Initial OS Timer for time ticks --- 初始化時間節拍定時器。
void InitOSTimer(void)
{
  TIMSK |= (1<<1);     // set T0IE0
  TCCR0  = 0x05;       // CTC0=CK/1024
  TCNT0  = T0_TCNT0;   // (256 - (T0_RELOAD & 0xff))
  SREG  |= (1<<7);     // SEI
}

//建立一個任務(Create a Task)。
//Inport :  tFunc --- function address , tStk --- stack bottom , prio --- Priority .
void OSTaskCreate (void (*tFunc)(void) , OS_STK *tStk, INT8U prio) 
{
 	OSTCB[prio].OSTaskStatus = OS_TASK_Rdy;
	OSTCB[prio].OSStkTop = (INT16U)tStk-1 /* Initial value when main was called             */
                          -12             /* reserve for to save R0-R5 , R26-R31 registers  */
                          -sizeof(INT16U) /* The PC value to be loaded                      */
					   ;
	*--tStk	=  *(INT16U const *)tFunc & 0xff;   /* Save low byte of task function address   */
	*--tStk	=  *(INT16U const *)tFunc / 0x100;  /* Save high byte of task function address  */
}

static unsigned int SaveSP; //用于保存需恢復的SP,在OSTickISR或用戶中斷結束做任務切換時，恢復SP.

//context switch interrupt --- 軟中斷任務切換
void OSCtxSw(void) 
{
    asm("PUSH R31\n"
        "PUSH R30\n"
        "PUSH R29\n"
        "PUSH R28\n"
        "PUSH R27\n"
        "PUSH R26\n"

        "PUSH R0\n"
        "PUSH R1\n"
        "PUSH R2\n"
        "PUSH R3\n"
        "PUSH R4\n"
        "PUSH R5\n"

		"IN R31,0x3d\n"     //Save SPL
		"STS %SaveSP,R31\n"
		"IN R31,0x3e\n"     //Save SPH 
		"STS %SaveSP+1,R31\n"
	
	);

	OSTCB[OS_TASK_CrtPrio].OSStkTop = SaveSP; //Save the current task top.

	OS_TASK_CrtPrio=OS_TASK_HighPri;

// Load context from the stack
    SaveSP = OSTCB[OS_TASK_CrtPrio].OSStkTop;	//load the high priority task task top.

    asm("CLI\n"						
	    "LDS R31,%SaveSP\n" 
	    "OUT 0x3d,R31\n"
		"LDS R31,%SaveSP+1\n" 
	    "OUT 0x3e,R31\n"
		"SEI\n"
		
        "POP R5\n"
        "POP R4\n"
        "POP R3\n"
        "POP R2\n"
        "POP R1\n"
        "POP R0\n"
		
	    "POP R26\n"
	    "POP R27\n"
        "POP R28\n"
        "POP R29\n"
        "POP R30\n"
        "POP R31\n"
	);
}
//Initial CPU SP for main() function stack.
void OSInitSP(void)
{
    SaveSP = (INT16U)&TASK_main_PrioStk[MAX_STK_SIZE-1];	//load the high priority task task top.
    asm("POP R0\n"
	    "POP R1\n"
	    "LDS R31,%SaveSP\n" 
	    "OUT 0x3d,R31\n"
		"LDS R31,%SaveSP+1\n" 
	    "OUT 0x3e,R31\n"
		"PUSH R1\n"
		"PUSH R0\n"
	);
}

//OS Time Tick Interrupt,OS 時鐘節拍中斷.
void OSTickISR(void) 
{
    TCNT0  = T0_TCNT0;   // (256 - (T0_RELOAD & 0xff))
	AppTickHook();     //Hook file for a time tick --- 用戶每個時間節拍的鉤子函數