📄 sch51.lst
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C51 COMPILER V6.10 SCH51 04/18/2001 16:29:38 PAGE 1
C51 COMPILER V6.10, COMPILATION OF MODULE SCH51
OBJECT MODULE PLACED IN .\SCH51.OBJ
COMPILER INVOKED BY: C:\KEIL\C51\BIN\C51.EXE .\SCH51.C OPTIMIZE(6,SPEED) BROWSE DEBUG OBJECTEXTEND SYMBOLS
stmt level source
1 /*------------------------------------------------------------------*-
2
3 SCH51.C (v1.00)
4
5 ------------------------------------------------------------------
6
7 *** THESE ARE THE CORE SCHEDULER FUNCTIONS ***
8 --- These functions may be used with all 8051 devices ---
9
10 *** SCH_MAX_TASKS *must* be set by the user ***
11 --- see "Sch51.H" ---
12
13 *** Includes (optional) power-saving mode ***
14 --- You must ensure that the power-down mode is adapted ---
15 --- to match your chosen device (or disabled altogether) ---
16
17
18 COPYRIGHT
19 ---------
20
21 This code is from the book:
22
23 PATTERNS FOR TIME-TRIGGERED EMBEDDED SYSTEMS by Michael J. Pont
24 [Pearson Education, 2001; ISBN: 0-201-33138-1].
25
26 This code is copyright (c) 2001 by Michael J. Pont.
27
28 See book for copyright details and other information.
29
30 -*------------------------------------------------------------------*/
31
32 #include "Main.h"
33 #include "Port.h"
34
35 #include "Sch51.h"
36
37 // ------ Public variable definitions ------------------------------
38
39 // The array of tasks
40 sTask SCH_tasks_G[SCH_MAX_TASKS];
41
42 // Used to display the error code
43 // See Main.H for details of error codes
44 // See Port.H for details of the error port
45 tByte Error_code_G = 0;
46
47 // ------ Private function prototypes ------------------------------
48
49 static void SCH_Go_To_Sleep(void);
50
51 // ------ Private variables ----------------------------------------
52
53 // Keeps track of time since last error was recorded (see below)
54 static tWord Error_tick_count_G;
55
C51 COMPILER V6.10 SCH51 04/18/2001 16:29:38 PAGE 2
56 // The code of the last error (reset after ~1 minute)
57 static tByte Last_error_code_G;
58
59
60 /*------------------------------------------------------------------*-
61
62 SCH_Dispatch_Tasks()
63
64 This is the 'dispatcher' function. When a task (function)
65 is due to run, SCH_Dispatch_Tasks() will run it.
66 This function must be called (repeatedly) from the main loop.
67
68 -*------------------------------------------------------------------*/
69 void SCH_Dispatch_Tasks(void)
70 {
71 1 tByte Index;
72 1
73 1 // Dispatches (runs) the next task (if one is ready)
74 1 for (Index = 0; Index < SCH_MAX_TASKS; Index++)
75 1 {
76 2 if (SCH_tasks_G[Index].RunMe > 0)
77 2 {
78 3 (*SCH_tasks_G[Index].pTask)(); // Run the task
79 3
80 3 SCH_tasks_G[Index].RunMe -= 1; // Reset / reduce RunMe flag
81 3
82 3 // Periodic tasks will automatically run again
83 3 // - if this is a 'one shot' task, remove it from the array
84 3 if (SCH_tasks_G[Index].Period == 0)
85 3 {
86 4 SCH_Delete_Task(Index);
87 4 }
88 3 }
89 2 }
90 1
91 1 // Report system status
92 1 SCH_Report_Status();
93 1
94 1 // The scheduler enters idle mode at this point
95 1 SCH_Go_To_Sleep();
96 1 }
97
98 /*------------------------------------------------------------------*-
99
100 SCH_Add_Task()
101
102 Causes a task (function) to be executed at regular intervals
103 or after a user-defined delay
104
105 Fn_P - The name of the function which is to be scheduled.
106 NOTE: All scheduled functions must be 'void, void' -
107 that is, they must take no parameters, and have
108 a void return type.
109
110 DELAY - The interval (TICKS) before the task is first executed
111
112 PERIOD - If 'PERIOD' is 0, the function is only called once,
113 at the time determined by 'DELAY'. If PERIOD is non-zero,
114 then the function is called repeatedly at an interval
115 determined by the value of PERIOD (see below for examples
116 which should help clarify this).
117
C51 COMPILER V6.10 SCH51 04/18/2001 16:29:38 PAGE 3
118
119 RETURN VALUE:
120
121 Returns the position in the task array at which the task has been
122 added. If the return value is SCH_MAX_TASKS then the task could
123 not be added to the array (there was insufficient space). If the
124 return value is < SCH_MAX_TASKS, then the task was added
125 successfully.
126
127 Note: this return value may be required, if a task is
128 to be subsequently deleted - see SCH_Delete_Task().
129
130 EXAMPLES:
131
132 Task_ID = SCH_Add_Task(Do_X,1000,0);
133 Causes the function Do_X() to be executed once after 1000 sch ticks.
134
135 Task_ID = SCH_Add_Task(Do_X,0,1000);
136 Causes the function Do_X() to be executed regularly, every 1000 sch ticks.
137
138 Task_ID = SCH_Add_Task(Do_X,300,1000);
139 Causes the function Do_X() to be executed regularly, every 1000 ticks.
140 Task will be first executed at T = 300 ticks, then 1300, 2300, etc.
141
142 -*------------------------------------------------------------------*/
143 tByte SCH_Add_Task(void (code * pFunction)(),
144 const tWord DELAY,
145 const tWord PERIOD)
146 {
147 1 tByte Index = 0;
148 1
149 1 // First find a gap in the array (if there is one)
150 1 while ((SCH_tasks_G[Index].pTask != 0) && (Index < SCH_MAX_TASKS))
151 1 {
152 2 Index++;
153 2 }
154 1
155 1 // Have we reached the end of the list?
156 1 if (Index == SCH_MAX_TASKS)
157 1 {
158 2 // Task list is full
159 2 //
160 2 // Set the global error variable
161 2 Error_code_G = ERROR_SCH_TOO_MANY_TASKS;
162 2
163 2 // Also return an error code
164 2 return SCH_MAX_TASKS;
165 2 }
166 1
167 1 // If we're here, there is a space in the task array
168 1 SCH_tasks_G[Index].pTask = pFunction;
169 1
170 1 SCH_tasks_G[Index].Delay = DELAY;
171 1 SCH_tasks_G[Index].Period = PERIOD;
172 1
173 1 SCH_tasks_G[Index].RunMe = 0;
174 1
175 1 return Index; // return position of task (to allow later deletion)
176 1 }
177
178 /*------------------------------------------------------------------*-
179
C51 COMPILER V6.10 SCH51 04/18/2001 16:29:38 PAGE 4
180 SCH_Delete_Task()
181
182 Removes a task from the scheduler. Note that this does
183 *not* delete the associated function from memory:
184 it simply means that it is no longer called by the scheduler.
185
186 TASK_INDEX - The task index. Provided by SCH_Add_Task().
187
188 RETURN VALUE: RETURN_ERROR or RETURN_NORMAL
189
190 -*------------------------------------------------------------------*/
191 bit SCH_Delete_Task(const tByte TASK_INDEX)
192 {
193 1 bit Return_code;
194 1
195 1 if (SCH_tasks_G[TASK_INDEX].pTask == 0)
196 1 {
197 2 // No task at this location...
198 2 //
199 2 // Set the global error variable
200 2 Error_code_G = ERROR_SCH_CANNOT_DELETE_TASK;
201 2
202 2 // ...also return an error code
203 2 Return_code = RETURN_ERROR;
204 2 }
205 1 else
206 1 {
207 2 Return_code = RETURN_NORMAL;
208 2 }
209 1
210 1 SCH_tasks_G[TASK_INDEX].pTask = 0x0000;
211 1 SCH_tasks_G[TASK_INDEX].Delay = 0;
212 1 SCH_tasks_G[TASK_INDEX].Period = 0;
213 1
214 1 SCH_tasks_G[TASK_INDEX].RunMe = 0;
215 1
216 1 return Return_code; // return status
217 1 }
218
219
220 /*------------------------------------------------------------------*-
221
222 SCH_Report_Status()
223
224 Simple function to display error codes.
225
226 This version displays code on a port with attached LEDs:
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