Microprocessors and Embedded Systems
Core concepts
Understand microprocessor architecture: ALU, registers, control unit, buses, and memory mapping. Know instruction formats, addressing modes, and the fetch-decode-execute cycle. Interrupts (maskable, non-maskable, vectored), DMA, and timing diagrams are frequent. For embedded systems, study microcontrollers, GPIO, timers, ADC, serial protocols (UART, SPI, I2C), and real-time constraints. Understand memory organisation, stack operations, and C-level bit manipulation.
Traps examiners set
- Interrupt latency includes saving context, not just the interrupt service routine.
- A maskable interrupt can be disabled; NMI cannot.
- In I2C, the master generates the clock; SPI has separate clock and data lines with no addressing.
- Stack grows downward in many architectures; pushing decreases the stack pointer.
- Polling wastes CPU time; interrupts free it.
Worked rule of thumb
For a UART at 9600 baud with 8N1 framing (10 bits per character), throughput is 960 characters per second. Doubling the baud rate doubles throughput but requires matching both ends. Always confirm clock source and divisor settings before trusting the link.
Practice strategy
Trace a small program's register and memory state step by step; it reveals addressing-mode mistakes.