?? sci_ti2s.lst
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C51 COMPILER V6.10 SCI_TI2S 04/18/2001 16:53:01 PAGE 1
C51 COMPILER V6.10, COMPILATION OF MODULE SCI_TI2S
OBJECT MODULE PLACED IN .\SCI_TI2S.OBJ
COMPILER INVOKED BY: C:\KEIL\C51\BIN\C51.EXE .\SCI_TI2S.C BROWSE DEBUG OBJECTEXTEND
stmt level source
1 /*------------------------------------------------------------------*-
2
3 SCI_Ti2s.c (v1.00)
4
5 ------------------------------------------------------------------
6
7 This is an implementation of SCI SCHEDULER (TICK) for 8051/52.
8
9 --- See Chapter 26 ---
10
11 *** SLAVE NODE : TICK-ONLY (DUPLEX) ***
12 *** MASTER CHECKS FOR SLAVE ACKNOWLEDEMENTS ***
13
14 *** Uses 1232 watchdog timer ***
15
16 *** Both Master and Slave share the same tick rate (1 ms) ***
17 *** - See Master code for details ***
18
19
20 COPYRIGHT
21 ---------
22
23 This code is from the book:
24
25 PATTERNS FOR TIME-TRIGGERED EMBEDDED SYSTEMS by Michael J. Pont
26 [Pearson Education, 2001; ISBN: 0-201-33138-1].
27
28 This code is copyright (c) 2001 by Michael J. Pont.
29
30 See book for copyright details and other information.
31
32 -*------------------------------------------------------------------*/
33
34 #include "Main.h"
35 #include "Port.h"
36
37 #include "SCI_Ti2s.h"
38 #include "TLight_A.h"
39
40 // ------ Public variable declarations -----------------------------
41
42 // The array of tasks (see Sch51.c)
43 extern sTask SCH_tasks_G[SCH_MAX_TASKS];
44
45 // The error code variable (see Sch51.c)
46 extern tByte Error_code_G;
47
48 // ------ Private function prototypes ------------------------------
49
50 static void SCI_TICK2_SLAVE_Enter_Safe_State(void);
51
52 static void SCI_TICK2_SLAVE_Watchdog_Init(void);
53 static void SCI_TICK2_SLAVE_Watchdog_Refresh(void) reentrant;
54
55 /*------------------------------------------------------------------*-
C51 COMPILER V6.10 SCI_TI2S 04/18/2001 16:53:01 PAGE 2
56
57 SCI_TICK2_SLAVE_Init()
58
59 Scheduler initialisation function. Prepares scheduler
60 data structures and sets up timer interrupts at required rate.
61
62 Must call this function before using the scheduler.
63
64 -*------------------------------------------------------------------*/
65 void SCI_TICK2_SLAVE_Init(void)
66 {
67 1 tByte i;
68 1
69 1 // Sort out the tasks
70 1 for (i = 0; i < SCH_MAX_TASKS; i++)
71 1 {
72 2 SCH_Delete_Task(i);
73 2 }
74 1
75 1 // Reset the global error variable
76 1 // - SCH_Delete_Task() will generate an error code,
77 1 // (because the task array is empty)
78 1 Error_code_G = 0;
79 1
80 1 // ---------- External interrupt 0 ----------
81 1 // The slave is driven by an interrupt input
82 1 // The interrupt is enabled
83 1 // It is triggered by a falling edge at pin P3.2
84 1 IT0 = 1;
85 1 EX0 = 1;
86 1
87 1 // Start the watchdog
88 1 SCI_TICK2_SLAVE_Watchdog_Init();
89 1 }
90
91 /*------------------------------------------------------------------*-
92
93 SCI_TICK2_SLAVE_Start()
94
95 Starts the slave scheduler, by enabling interrupts.
96
97 NOTE: Usually called after all regular tasks are added,
98 to keep the tasks synchronised.
99
100 NOTE: ONLY THE SCHEDULER INTERRUPT SHOULD BE ENABLED!!!
101
102 -*------------------------------------------------------------------*/
103 void SCI_TICK2_SLAVE_Start(void)
104 {
105 1 // Place system in a safe state
106 1 // - slave will keep returning here if master does not start
107 1 // - or otherwise fails.
108 1 SCI_TICK2_SLAVE_Enter_Safe_State();
109 1
110 1 // Now in a safe state
111 1 // Wait here - indefinitely - for the first tick
112 1 // (Refresh the watchdog to avoid constant watchdog restarts)
113 1 while (IE0 == 0)
114 1 {
115 2 SCI_TICK2_SLAVE_Watchdog_Refresh();
116 2 }
117 1
C51 COMPILER V6.10 SCI_TI2S 04/18/2001 16:53:01 PAGE 3
118 1 // Clear the flag
119 1 IE0 = 0;
120 1
121 1 // Start the scheduler
122 1 EA = 1;
123 1 }
124
125 /*------------------------------------------------------------------*-
126
127 SCI_TICK2_SLAVE_Update
128
129 This is the scheduler ISR. It is called at a rate
130 determined by the timer settings in SCI_TICK2_SLAVE_Init().
131
132 This Slave is triggered by external interrupts.
133
134 -*------------------------------------------------------------------*/
135 void SCI_TICK2_SLAVE_Update(void) interrupt INTERRUPT_EXTERNAL_0
136 {
137 1 tByte Index;
138 1
139 1 // Feed the watchdog
140 1 // Master will monitor this pin to check for slave activity
141 1 SCI_TICK2_SLAVE_Watchdog_Refresh();
142 1
143 1 // Now do 'standard' scheduler updates
144 1
145 1 // NOTE: calculations are in *TICKS* (not milliseconds)
146 1 for (Index = 0; Index < SCH_MAX_TASKS; Index++)
147 1 {
148 2 // Check if there is a task at this location
149 2 if (SCH_tasks_G[Index].pTask)
150 2 {
151 3 if (SCH_tasks_G[Index].Delay == 0)
152 3 {
153 4 // The task is due to run
154 4 SCH_tasks_G[Index].RunMe += 1; // Incr. the run flag
155 4
156 4 if (SCH_tasks_G[Index].Period)
157 4 {
158 5 // Schedule this periodic task to run again
159 5 SCH_tasks_G[Index].Delay = SCH_tasks_G[Index].Period;
160 5 }
161 4 }
162 3 else
163 3 {
164 4 // Not yet ready to run: just decrement the delay
165 4 SCH_tasks_G[Index].Delay -= 1;
166 4 }
167 3 }
168 2 }
169 1 }
170
171 /*------------------------------------------------------------------*-
172
173 SCI_TICK2_SLAVE_Watchdog_Init()
174
175 This function sets up the watchdog timer.
176
177 If the Master fails (or other error develop),
178 no tick messages will arrive, and the scheduler
179 will stop.
C51 COMPILER V6.10 SCI_TI2S 04/18/2001 16:53:01 PAGE 4
180
181 To detect this situation, we have a (hardware) watchdog
182 running in the slave. This watchdog - which should be set to
183 overflow at around 100ms - is used to set the system into a
184 known (safe) state. The slave will then wait (indefinitely)
185 for the problem to be resolved.
186
187 NOTE: The slave will not be generating Ack messages in these
188 circumstances. The Master (if running) will therefore be aware
189 that there is a problem.
190
191 -*------------------------------------------------------------------*/
192 void SCI_TICK2_SLAVE_Watchdog_Init(void)
193 {
194 1 // INIT NOT REQUIRED FOR 1232 EXTERNAL WATCHDOG
195 1 // - May be required wwith different watchdog hardware
196 1 //
197 1 // Edit as required
198 1 }
199
200
201 /*------------------------------------------------------------------*-
202
203 SCI_TICK2_SLAVE_Watchdog_Refresh()
204
205 Feed the external (1232) watchdog.
206
207 Timeout is between ~60 and 250 ms (hardware dependent)
208
209 HARDWARE: Assumes external 1232 watchdog
210
211 -*------------------------------------------------------------------*/
212 void SCI_TICK2_SLAVE_Watchdog_Refresh(void) reentrant
213 {
214 1 static bit WATCHDOG_state;
215 1
216 1 // Change the state of the watchdog pin
217 1 if (WATCHDOG_state == 1)
218 1 {
219 2 WATCHDOG_state = 0;
220 2 WATCHDOG_pin = 0;
221 2 }
222 1 else
223 1 {
224 2 WATCHDOG_state = 1;
225 2 WATCHDOG_pin = 1;
226 2 }
227 1 }
228
229 /*------------------------------------------------------------------*-
230
231 SCI_TICK2_SLAVE_Enter_Safe_State()
232
233 This is the state enterted by the system when:
234 (1) The node is powered up or reset
235 (2) The Master node fails
236 (3) The network has an error
237 (4) Tick messages are delayed for any other reason
238
239 Try to ensure that the system is in a 'safe' state in these
240 circumstances.
241
C51 COMPILER V6.10 SCI_TI2S 04/18/2001 16:53:01 PAGE 5
242 -*------------------------------------------------------------------*/
243 void SCI_TICK2_SLAVE_Enter_Safe_State(void)
244 {
245 1 // USER DEFINED - Edit as required
246 1 TRAFFIC_LIGHTS_Display_Safe_Output();
247 1 }
248
249 /*------------------------------------------------------------------*-
250 ---- END OF FILE -------------------------------------------------
251 -*------------------------------------------------------------------*/
252
MODULE INFORMATION: STATIC OVERLAYABLE
CODE SIZE = 210 ----
CONSTANT SIZE = ---- ----
XDATA SIZE = ---- ----
PDATA SIZE = ---- ----
DATA SIZE = ---- 1
IDATA SIZE = ---- ----
BIT SIZE = 1 ----
END OF MODULE INFORMATION.
C51 COMPILATION COMPLETE. 0 WARNING(S), 0 ERROR(S)
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