4th Semseter files

4th-Semester-Spring-2023/Embedded/Lectures/Lecture07/notes.md

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+# Intro to Embedded Systems Lecture Notes: February 7th, 2023
+
+## Using Interrupts
+```c
+#define INTERRUPT_PINS 0x03
+
+int main(void)
+{
+    P4IE |= INTERRUPT_PINS;                                     // Local interrupt enable
+    P4IFG |= INTERRUPT_PINS;
+    P4IES |= INTERRUPT_PINS;
+
+    _enable_interrupts();                                       // Global interrupt enable
+    __bis_SR_register(GIE);
+
+    while (true)
+    {
+        ...
+    }
+     return 0;
+}
+
+// Port 4 interrupt service routine
+void __attribute__ ((interrupt(PORT4_VECTOR))) Port_4 (void)
+{
+    ...
+}
+```
+
+## Interrupt Servicing Summary
+1. Interrupt Pending
+2. Complete Current Instruction
+3. Clear SR
+4. Retrieve starting address of ISR & put address in PC
+5. Execute ISR
+6. Pop SR and PC from stack
+7. Continue to main program
+
+## Multiple Interrupts
+### Three Types:
+1. Reset Interrupt
+2. Maskable Interrupt
+    - ADC, port, timer, e_USCI
+    - User-asserted event
+3. Non-Maskable Interrupt
+    - Fault, error detection
+    - Oscillator fault
+    - Flash key violation
+
+## Priority of Interrupts
+1. Timers
+2. e_USCI
+3. ADC
+4. Port