Timers in Assembly Language

Assembly Language doesn’t have built-in timer functionality or high-level concepts like channels. However, we can simulate a basic timer using a loop and a system call to sleep. Here’s a simplified version of the timer concept in x86 Assembly for Linux:

section .data
    msg1 db "Timer 1 fired", 0
    msg2 db "Timer 2 stopped", 0

section .text
    global _start

_start:
    ; Simulate Timer 1 (2 seconds)
    mov ecx, 2  ; Set counter to 2 (2 seconds)
timer1_loop:
    push ecx
    mov eax, 162  ; nanosleep system call number
    mov ebx, timespec
    xor ecx, ecx
    int 0x80  ; Invoke system call
    pop ecx
    loop timer1_loop

    ; Print "Timer 1 fired"
    mov eax, 4  ; write system call number
    mov ebx, 1  ; file descriptor (stdout)
    mov ecx, msg1
    mov edx, 14  ; message length
    int 0x80

    ; Simulate stopping Timer 2
    mov eax, 4
    mov ebx, 1
    mov ecx, msg2
    mov edx, 16
    int 0x80

    ; Exit program
    mov eax, 1  ; exit system call number
    xor ebx, ebx
    int 0x80

section .data
    timespec:
        dd 1  ; 1 second
        dd 0  ; 0 nanoseconds

This Assembly code simulates the basic concept of timers:

1. We define two messages: “Timer 1 fired” and “Timer 2 stopped”.

2. The program starts by simulating Timer 1. It uses a loop that calls the nanosleep system call twice, each time sleeping for 1 second. This simulates waiting for 2 seconds.

3. After the timer “fires” (the loop completes), we print “Timer 1 fired” using the write system call.

4. We then immediately print “Timer 2 stopped”, simulating the cancellation of the second timer before it fires.

5. Finally, the program exits using the exit system call.

To run this program:

1. Save the code in a file named timers.asm.
2. Assemble and link the program:

$ nasm -f elf timers.asm
$ ld -m elf_i386 -o timers timers.o

3. Run the program:

$ ./timers
Timer 1 fired
Timer 2 stopped

This Assembly example demonstrates a very basic simulation of timers. It doesn’t include features like concurrent execution or actual timer cancellation, as these concepts are much more complex to implement in low-level Assembly. In real-world scenarios, timers and more advanced timing operations would typically be handled by the operating system or higher-level libraries.