RTOS implementation header file - EE.StackExchange

/*
 * File:   RTOS.h
 * Author: abdullah
 *
 * Created on 21 Haziran 2012 Perşembe, 10:51
 */

#ifndef RTOS_H
#define RTOS_H

#define OS_yield(); {\
asm("movlw   _OS_tasks            ; Store the address of tasks, which is the start address of our task 'array'."); \
asm("addwf   _OS_currentTask, w   ; Add current task's index to the start address."); \
asm("movwf   fsr                  ; We have the index of current task in W. Copy it to FSR"); \
asm("movf    pclath, w            ; Copy PCLATH register's contents to W register."); \
asm("movwf   indf                 ; Copy W to current task's first item. We now store PCLATH of the current state of the task."); \
asm("incf    fsr, f               ; Increment index, so that we will point to the next item of current task."); \
asm("movlw   low($+3)             ; Copy PCL+3 to W register. This will let us save the PCL of the current state of the task."); \
asm("movwf   indf                 ; Copy W to task's next item. With that, we will initialize the current task."); \
asm("goto    _OS_taskswitcher     ; Yield the CPU to the awaiting task by going to task switcher."); \
}
#define OS_initializeTask(); {\
asm("movlw   _OS_tasks            ; Store the address of tasks, which is the start address of our task 'array'."); \
asm("addwf   _OS_currentTask, w   ; Add current task's index to the start address."); \
asm("movwf   fsr                  ; We have the index of current task in W. Copy it to FSR"); \
asm("movf    pclath, w            ; Copy PCLATH register's contents to W register."); \
asm("movwf   indf                 ; Copy W to current task's first item. We now store PCLATH."); \
asm("incf    fsr,f                ; Increment index, so that we will point to the next item of current task."); \
asm("movlw   low($+3)             ; Copy PCL+3 to W register. This will let us save the PCL of the start of the task."); \
asm("movwf   indf                 ; Copy W to task's next item. With that, we will initialize the current task."); \
asm("return                       ; We have gathered our initialazation information. Return back to main."); \
}
#define OS_runTasks(numberOfTasks); {\
asm("_OS_taskswitcher"); \
asm("movlw   0x02                 ; W = 2"); \
asm("addwf   _OS_currentTask, f   ; Add 2 to currentTask, store it in currentTask."); \
asm("movlw   "#numberOfTasks"     ; W = numOfTasks"); \
asm("subwf   _OS_currentTask, w   ; w= f - w"); \
asm("btfsc   status, 0            ; If currentTask >= numOfTasks"); \
asm("clrf    _OS_currentTask      ; Clear currentTask"); \
asm("movlw   _OS_tasks            ; Store the address of tasks, which is the start address of our task 'array'."); \
asm("addwf   _OS_currentTask, w   ; Add current task's index to the start address."); \
asm("movwf   fsr                  ; We have the index of current task in W. Copy it to FSR"); \
asm("movf    indf, w              ; Copy the contents of current task's first item to W"); \
asm("movwf   pclath               ; Copy W to PCLATH. As a result, current task's PCLATH will be in PCLATH register."); \
asm("incf    fsr, f               ; Increment index, so that we will point to the next item of current task."); \
asm("movf    indf, w              ; Copy the contents of current task's second item to W."); \
asm("movwf   pcl                  ; Copy W to PCL. Finally, current task's PCL will be in PCL register."); \
}

#endif  /* RTOS_H */