Memory-to-peripheral transfer in Embedded C - Time & Space Complexity

Time Complexity: Memory-to-peripheral transfer

O(n)

Understanding Time Complexity

When transferring data from memory to a peripheral device, it is important to understand how the time taken grows as the amount of data increases.

We want to know how the number of operations changes when we send more data.

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

void transfer_data(uint8_t *memory, volatile uint8_t *peripheral, int size) {
    for (int i = 0; i < size; i++) {
        peripheral[i] = memory[i];
    }
}
    

This code copies data byte-by-byte from a memory array to a peripheral device buffer.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: The for-loop that copies each byte from memory to peripheral.
• How many times: The loop runs exactly size times, once for each byte.

How Execution Grows With Input

As the amount of data to transfer grows, the number of copy operations grows in the same way.

Input Size (n)	Approx. Operations
10	10 copy operations
100	100 copy operations
1000	1000 copy operations

Pattern observation: The number of operations grows directly with the input size; doubling the data doubles the work.

Final Time Complexity

Time Complexity: O(n)

This means the time to transfer data grows linearly with the amount of data.

Common Mistake

[X] Wrong: "The transfer time stays the same no matter how much data we send."

[OK] Correct: Each byte must be copied individually, so more data means more time.

Interview Connect

Understanding how data transfer time grows helps you explain performance in embedded systems clearly and confidently.

Self-Check

"What if we used DMA (Direct Memory Access) instead of a loop? How would the time complexity change?"