4th Semseter files

4th-Semester-Spring-2023/Embedded/Lectures/Lecture05/notes.md

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+# Intro to Embedded Systems Lecture Notes: January 31st, 2023
+
+## POLLING
+
+**Initialize the port**
+
+Output:
+```c
+    P6DIR |= BIT6;
+    P6OUT &= ~BIT6;
+```
+Input:
+```c
+    P4DIR &= ~BIT1;
+```
+Clear LOCKLPM5 (Lock low-power mode) from PMCTL0 (Power management control):
+```c
+   PMCTL0 &= ~LOCKLPM5;
+```
+
+Program the board
+
+**Floating condition: not 1 or 0**
+        Fix using pull-up/pull-down resistor
+ 
+## PULL-UP / PULL-DOWN RESISTORS
+
+**Pull-up resesistor**
+- Active Low
+- Mostly preferrable for MCUs
+- Safety -> reduces noise
+
+**Pull-down resistor**
+- Active high
+
+## I/O Configuration
+
+
+| P<sub>x</sub>DIR | P<sub>x</sub>REN | P<sub>x</sub>OUT | Comment        |
+|-------|-------|-------|----------------|
+|    0  |     0 |     X | Input          |
+|    0  |     1 |     0 | Input with PDR |
+|    0  |     1 |     1 | Input with PUR |
+|    1  |     X |     X | Output         |
+
+## LOW POWER MODE
+
+| SCG<sub>1 | SCG<sub>0 | OSC OFF | CPU OFF | Mode     |
+|------|------|---------|---------|----------|
+|    0 |    0 |       0 |       0 | Active   |
+|    0 |    0 |       0 |       1 | LPM0     |
+|    0 |    1 |       0 |       1 | LPM1     |
+|    1 |    0 |       0 |       1 | LPM2     |
+|    1 |    1 |       0 |       1 | LPM3     |
+|    1 |    1 |       1 |       1 | LPM4     | 
+
+## WHEN INTERRUPT HAPPENS
+- Processor stops what it's doing
+- Stores information to later resume
+- Executes interrupt service routine (ISR)
+- Restores saved information
+- Resumes execution