Interrupts - Revision history

LIMS at 22:02, 25 July 2008

2008-07-25T22:02:30Z

LIMS at 21:54, 25 July 2008

2008-07-25T21:54:29Z

LIMS at 21:46, 25 July 2008

2008-07-25T21:46:57Z

LIMS at 21:44, 25 July 2008

2008-07-25T21:44:09Z

LIMS at 21:42, 25 July 2008

2008-07-25T21:42:51Z

LIMS at 21:42, 25 July 2008

2008-07-25T21:42:04Z

LIMS at 21:41, 25 July 2008

2008-07-25T21:41:18Z

LIMS at 21:39, 25 July 2008

2008-07-25T21:39:31Z

LIMS at 21:38, 25 July 2008

2008-07-25T21:38:42Z

LIMS at 21:37, 25 July 2008

2008-07-25T21:37:14Z

← Older revision		Revision as of 22:02, 25 July 2008
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	One disadvantage is that sometimes an interrupt will be missed because the timer trips while interrupts are disabled~~. The consequences of this behavior depends on your application~~.		One disadvantage is that sometimes an interrupt will be missed because the timer trips while interrupts are disabled.

← Older revision		Revision as of 21:54, 25 July 2008
Line 48:		Line 48:


	One disadvantage is that sometimes an interrupt will be missed because the timer trips while interrupts are disabled~~. If this happens, the timing of the interrupts should not be phase-shifted -- one will just be missing~~. The consequences of this behavior depends on your application.		One disadvantage is that sometimes an interrupt will be missed because the timer trips while interrupts are disabled. The consequences of this behavior depends on your application.

← Older revision		Revision as of 21:46, 25 July 2008
Line 48:		Line 48:


	One disadvantage is that sometimes an interrupt will be missed because the timer trips while interrupts are disabled. The consequences of this behavior depends on your application.		One disadvantage is that sometimes an interrupt will be missed because the timer trips while interrupts are disabled. If this happens, the timing of the interrupts should not be phase-shifted -- one will just be missing. The consequences of this behavior depends on your application.

@@ Line 25: / Line 25: @@
 USING THE SAME VARIABLE IN BOTH THE INTERRUPT AND THE MAIN CODE WILL GENERATE ELUSIVE BUGS
-If a variable, X, is being updated in your interrupt routine, you cannot reliably use that variable in your main code.  Not even for seemingly benign operations such as conditionals (i.e. if (X<3){...} ).  You can work around this problem by disabling interrupts before referencing the variable and re-enabling them after using it.
+If a variable, X, is being updated in your interrupt routine, you cannot reliably use that variable in your main code.  Not even for seemingly benign operations such as conditionals (i.e. if (X<3){...} ).  You can work around this problem by disabling interrupts before referencing the variable and then re-enabling them afterwards.
  //INTERRUPT ROUTINE

@@ Line 25: / Line 25: @@
 USING THE SAME VARIABLE IN BOTH THE INTERRUPT AND THE MAIN CODE WILL GENERATE ELUSIVE BUGS
-If a variable, X, is being updated in your interrupt routine, you cannot reliably use that variable in your main code.  Not even for seeming benign operations such as conditionals (i.e. if (X<3){...} ).  You can work around this problem by disabling interrupts before referencing the variable and re-enabling them after using it.
+If a variable, X, is being updated in your interrupt routine, you cannot reliably use that variable in your main code.  Not even for seemingly benign operations such as conditionals (i.e. if (X<3){...} ).  You can work around this problem by disabling interrupts before referencing the variable and re-enabling them after using it.
  //INTERRUPT ROUTINE

← Older revision		Revision as of 21:42, 25 July 2008
Line 48:		Line 48:


	One disadvantage is that sometimes an interrupt will be missed because the timer trips while interrupts are disabled. The ~~impact~~ of this ~~issue~~ depends on your application.		One disadvantage is that sometimes an interrupt will be missed because the timer trips while interrupts are disabled. The consequences of this behavior depends on your application.

← Older revision		Revision as of 21:41, 25 July 2008
Line 48:		Line 48:


	One disadvantage is that sometimes a interrupt will be missed because the timer trips while interrupts are disabled. The ~~seriousness~~ of this depends on your application.		One disadvantage is that sometimes an interrupt will be missed because the timer trips while interrupts are disabled. The impact of this issue depends on your application.

@@ Line 39: / Line 39: @@
   u16_X_MAIN = u16_X;        //access the interrupt variable only when interrupts are disabled
   enable_interrupts(GLOBAL);
+  ...
   if (u16_X_MAIN>20)         //the copy of the variable for the main code can be accessed at any time
      {u8_y = 1;}
   end
+  ...
   }
  }

@@ Line 27: / Line 27: @@
 If a variable, X, is being updated in your interrupt routine, you cannot reliably use that variable in your main code.  Not even for seeming benign operations such as conditionals (i.e. if (X<3){...} ).  You can work around this problem by disabling interrupts before referencing the variable and re-enabling them after using it.
+ //INTERRUPT ROUTINE
  #INT_TIMER2
  void Timer2isr() {
@@ Line 32: / Line 33: @@
    ...
    }
- //MAIN LOOP
+ //MAIN ROUTINE
  void main(void) {
   while(TRUE){

@@ Line 23: / Line 23: @@
 WARNING:
-USING THE SAME VARIABLE IN BOTH THE INTERRUPT AND THE MAIN CODE IS WILL GENERATE STRANGE BUGS
+USING THE SAME VARIABLE IN BOTH THE INTERRUPT AND THE MAIN CODE WILL GENERATE ELUSIVE BUGS
-If a variable, X, is being updated in your interrupt routine, you cannot reliably use that variable in your main code.  Not even for seeming benign operations such as conditionals (i.e. if (X<CONSTANT){...} ).  You can work around this problem by disabling interrupts before referencing the variable and re-enabling them after using it.
+If a variable, X, is being updated in your interrupt routine, you cannot reliably use that variable in your main code.  Not even for seeming benign operations such as conditionals (i.e. if (X<3){...} ).  You can work around this problem by disabling interrupts before referencing the variable and re-enabling them after using it.
  #INT_TIMER2
  void Timer2isr() {
-   //find the change in phase after the 1 ms has passed
+   u16_X += 3; //add 3 to X every time the interrupt is tripped
-   u16_X += 3;
    ...
    }
+ //MAIN LOOP
  void main(void) {
   while(TRUE){
@@ Line 38: / Line 38: @@
   u16_X_MAIN = u16_X;        //access the interrupt variable only when interrupts are disabled
   enable_interrupts(GLOBAL);
-  if (u16_X_MAIN>20)  //access the copy of the variable whenever you'd like
+  if (u16_X_MAIN>20)         //the copy of the variable for the main code can be accessed at any time
      {u8_y = 1;}
   end
@@ Line 45: / Line 45: @@
-The disadvantage is that sometimes a interrupt will be missed because the timer trips while interrupts are disabled.  The seriousness  of this depends on your application.
+One disadvantage is that sometimes a interrupt will be missed because the timer trips while interrupts are disabled.  The seriousness  of this depends on your application.