How does a microprocessor communicate with peripherals?

A microprocessor communicates with peripherals through a combination of data buses, address buses, control signals, and specific I/O techniques. The goal is to send data, receive input, and control external devices like sensors, displays, keyboards, and communication modules.

Main Components Involved

Communication Methods
1. Memory-Mapped I/O (MMIO)
Used by ARM (e.g., STM32), MIPS, RISC-V

• Peripherals are assigned memory addresses
• CPU uses normal instructions to access them (e.g., LDR, STR in ARM)
• Example: 0x40020000 could be a GPIO register

c

#define GPIO_DATA (*(volatile unsigned int *)0x40020000)
GPIO_DATA = 0xFF;  // Send data to GPIO

2. Port-Mapped I/O (PMIO)
Used by Intel x86 (e.g., 8086)

• Peripherals are in a separate I/O space
• Accessed with special instructions like IN, OUT

asm

mov dx, 0x03F8  ; COM1 serial port
mov al, 'A'
out dx, al      ; Send character to peripheral

Data Transfer Mechanisms

Control Signals Used

Visual Overview:

css

           ┌────────────────────────┐
           │      Microprocessor    │
           └──────┬────┬────┬───────┘
                  │    │    │
         ┌────────▼────▼────▼────────┐
         │  Address  Data  Control   │   ← Buses
         └────────┬────┬────┬────────┘
                  │    │    │
      ┌───────────▼┐  ┌▼───────────┐
      │  Memory    │  │ Peripheral │ ← (e.g., GPIO, UART, LCD)
      └────────────┘  └────────────┘

Summary