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/*
1		/*
2		* File: main.c
3		* Author: abdullah
4		*
5		* Created on 10 Haziran 2012 Pazar, 14:43
6		*/
7		#include <xc.h> // Include the header file needed by the compiler
8		__CONFIG(FOSC_INTOSCIO & WDTE_OFF & PWRTE_ON & MCLRE_OFF & CP_OFF & IOSCFS_4MHZ & BOREN_ON);
9
10		#define numOfTasks 4
11		unsigned char currentTask; // This TCB pointer will point to the current task's TCB.
12		unsigned char tasks[4];
13
14		void fTask1(void); // Prototype the function for task1.
15		void fTask2(void); // Prototype the function for task2.
16
17		void main(void)
18		{
19		TRISA = 0; // Set all of the PORTA pins as outputs.
20		TRISC = 0; // Set all of the PORTC pins as outputs.
21		ANSEL = 0; // Set all of the analog input pins as digital i/o.
22		PORTA = 0; // Clear PORTA bits.
23		PORTC = 0; // Clear PORTC bits.
24
25		currentTask = 0;
26		fTask1();
27	-	currentTask++;
27	+	currentTask+=2; // was "currentTask++;" before.
28		fTask2();
29
30		#asm
31		_taskswitcher
32		movlw 0x02 ; W = 2
33		addwf _currentTask, f ; Add 2 to currentTask, store it in currentTask.
34		movlw numOfTasks ; W = numOfTasks
35		subwf _currentTask, w ; w= f - w
36		btfsc status, 0 ; If currentTask >= numOfTasks
37		clrf _currentTask ; Clear currentTask
38
39		movlw _tasks ; Store the address of tasks, which is the start address of our task "array".
40		addwf _currentTask, w ; Add current task's index to the start address.
41		; For example; task1's index is 2: [task0_1][task0_2][task1_1][task1_2]....
42		; 0 1 2 3
43		movwf fsr ; We have the index of current task in W. Copy it to FSR
44		movf indf, w ; Copy the contents of current task's first item to W
45		movwf pclath ; Copy W to PCLATH. As a result, current task's PCLATH will be in PCLATH register.
46
47		incf fsr, f ; Increment index, so that we will point to the next item of current task.
48		movf indf, w ; Copy the contents of current task's second item to W.
49		movwf pcl ; Copy W to PCL. Finally, current task's PCL will be in PCL register.
50		#endasm
51		}
52
53		void fTask1(void)
54		{
55		#asm
56		movlw _tasks ; Store the address of tasks, which is the start address of our task "array".
57		addwf _currentTask, w ; Add current task's index to the start address.
58
59		movwf fsr ; We have the index of current task in W. Copy it to FSR
60		movf pclath, w ; Copy PCLATH register's contents to W register.
61		movwf indf ; Copy W to current task's first item. We now store PCLATH.
62
63		incf fsr,f ; Increment index, so that we will point to the next item of current task.
64		movlw low($+3) ; Copy PCL+3 to W register. This will let us save the PCL of the start of the task.
65		movwf indf ; Copy W to task's next item. With that, we will initialize the current task.
66		return ; We have gathered our initialazation information. Return back to main.
67		#endasm
68
69		while (1)
70		{
71		PORTA = 0xAA; // Toggle PORTA.0
72
73		#asm
74		movlw _tasks ; Store the address of tasks, which is the start address of our task "array".
75		addwf _currentTask, w ; Add current task's index to the start address.
76
77		movwf fsr ; We have the index of current task in W. Copy it to FSR
78		movf pclath, w ; Copy PCLATH register's contents to W register.
79		movwf indf ; Copy W to current task's first item. We now store PCLATH of the current state of the task.
80
81		incf fsr, f ; Increment index, so that we will point to the next item of current task.
82		movlw low($+3) ; Copy PCL+3 to W register. This will let us save the PCL of the current state of the task.
83		movwf indf ; Copy W to task's next item. With that, we will initialize the current task.
84
85		goto _taskswitcher ; Yield the CPU to the awaiting task by going to task switcher.
86		#endasm
87
88		PORTA = 0x55; // Toggle PORTA.0
89		}
90		}
91
92		void fTask2(void)
93		{
94		#asm
95		movlw _tasks ; Store the address of tasks, which is the start address of our task "array".
96		addwf _currentTask, w ; Add current task's index to the start address.
97
98		movwf fsr ; We have the index of current task in W. Copy it to FSR
99		movf pclath, w ; Copy PCLATH register's contents to W register.
100		movwf indf ; Copy W to current task's first item. We now store PCLATH.
101
102		incf fsr,f ; Increment index, so that we will point to the next item of current task.
103		movlw low($+3) ; Copy PCL+3 to W register. This will let us save the PCL of the start of the task.
104		movwf indf ; Copy W to task's next item. With that, we will initialize the current task.
105		return ; We have gathered our initialazation information. Return back to main.
106		#endasm
107
108		while (1)
109		{
110		PORTA = 0xAA; // Toggle PORTA.0
111
112		#asm
113		movlw _tasks ; Store the address of tasks, which is the start address of our task "array".
114		addwf _currentTask, w ; Add current task's index to the start address.
115
116		movwf fsr ; We have the index of current task in W. Copy it to FSR
117		movf pclath, w ; Copy PCLATH register's contents to W register.
118		movwf indf ; Copy W to current task's first item. We now store PCLATH of the current state of the task.
119
120		incf fsr, f ; Increment index, so that we will point to the next item of current task.
121		movlw low($+3) ; Copy PCL+3 to W register. This will let us save the PCL of the current state of the task.
122		movwf indf ; Copy W to task's next item. With that, we will initialize the current task.
123
124		goto _taskswitcher ; Yield the CPU to the awaiting task by going to task switcher.
125		#endasm
126
127		PORTA = 0x55; // Toggle PORTA.0
128		}
129		}