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README.md

Hardware Interactions

This README provides an explanation of a simple assembly program that demonstrates hardware interactions between switches and LEDs on a simulated device.

Assembly Code Explanation

The provided assembly code snippet performs direct memory access to interact with hardware components, specifically LEDs and switches. Here's a line-by-line breakdown:

  • .equ SWITCH, 0xff200040: This line sets up an alias named SWITCH for the memory address 0xff200040, which corresponds to the switches in the simulator.

  • .equ LED, 0xff200000: Similarly, LED is set as an alias for the memory address 0xff200000, representing the LEDs in the simulator.

  • .global _start: This directive indicates that _start is a global label, which is where program execution begins.

  • _start:: The entry point of the program.

  • LDR R0,=SWITCH: Load the address of SWITCH into register R0.

  • LDR R1,[R0]: Load the value from the address contained in R0 (the state of switches) into register R1.

  • LDR R0,=LED: Load the address of LED into register R0.

  • STR R1,[R0]: Store the value from register R1 into the address contained in R0 (which will update the state of LEDs).

Hardware Flow

When this code is executed:

  1. The current state of switches (on/off) is read into register R1.
  2. The same state is then written to LEDs, causing them to reflect the state of switches.

In essence, flipping a switch will turn on/off its corresponding LED.

Simulator Image Explanation

Simulator Interface

The image shows a simulator interface divided into two sections: "LEDs" and "Switches". Each section has its own set of addresses that correspond to physical components on an actual device.

  • LEDs: The indicators are at address 0xff200000. In this example, three LEDs are lit, indicating that their corresponding switches are turned on.
  • Switches: Located at address 0xff200040, several switches are in the 'on' position as indicated by checkmarks.

This visual representation helps understand how the code manipulates these components through memory-mapped I/O addresses.