This README provides an explanation of a simple assembly program that demonstrates hardware interactions between switches and LEDs on a simulated device.
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:
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.equ SWITCH, 0xff200040: This line sets up an alias namedSWITCHfor the memory address0xff200040, which corresponds to the switches in the simulator. -
.equ LED, 0xff200000: Similarly,LEDis set as an alias for the memory address0xff200000, representing the LEDs in the simulator. -
.global _start: This directive indicates that_startis a global label, which is where program execution begins. -
_start:: The entry point of the program. -
LDR R0,=SWITCH: Load the address ofSWITCHinto 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 ofLEDinto register R0. -
STR R1,[R0]: Store the value from register R1 into the address contained in R0 (which will update the state of LEDs).
When this code is executed:
- The current state of switches (on/off) is read into register R1.
- 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.
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.