1.4 KiB
Executable File
1.4 KiB
Executable File
Intro to Embedded Systems Lecture Notes: January 31st, 2023
POLLING
Initialize the port
Output:
P6DIR |= BIT6;
P6OUT &= ~BIT6;
Input:
P4DIR &= ~BIT1;
Clear LOCKLPM5 (Lock low-power mode) from PMCTL0 (Power management control):
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
| PxDIR | PxREN | PxOUT | Comment |
|---|---|---|---|
| 0 | 0 | X | Input |
| 0 | 1 | 0 | Input with PDR |
| 0 | 1 | 1 | Input with PUR |
| 1 | X | X | Output |
LOW POWER MODE
| SCG1 | SCG0 | 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