In embedded development, delay functions are fundamental operations. However, when faced with microsecond-level precision requirements, the choice between loop delays and timer solutions directly affects system stability.
1. Loop Delay: A Legacy from the Bare-Metal Era
Implementation Principle: Consumes CPU cycles through no-operation instructions (such as NOP) or decrement loops.
Critical Flaw:
Precision fluctuation > 50% (affected by compiler optimization and clock frequency).
Blocking design leads to 0% CPU utilization, unable to respond to interrupts.
Applicable Scenarios:
Simple delays during initialization (e.g., LED lighting tests).
Emergency solutions for cost-sensitive 8-bit MCUs (e.g., STC89C52).
2. Timer Delay: The Standard for Precision Era
Implementation Principle: Uses hardware timers to generate interrupts for non-blocking delays.
Core Advantages:
Precision reaches clock cycle level (e.g., a 24MHz MCU can achieve 0.041μs resolution).
100% CPU utilization, supporting multitasking in parallel.
Applicable Scenarios:
Timing for communication protocols (e.g., controlling I2C at 100kbps).
Real-time response scenarios such as motor control.
3. How to Choose Between Loop and Timer?
① When precision requirements > 1ms
Timer solutions are mandatory, as loop delay errors far exceed protocol tolerances (e.g., UART’s 1-bit width error > 5% will cause failure).
② Resource-constrained scenarios
For 8-bit MCUs without hardware timers, loop delays can be used, but compiler optimization must be disabled (e.g., GCC’s -O0 parameter).
③ Low-power design
Timer solutions support wake-up from sleep mode, while loop delays cause the CPU to run continuously, resulting in 2-3 orders of magnitude higher power consumption.
This article is an original piece by Fan Yi Education, please indicate the source when reprinting!