hello, does anyone know how to make a "delay", say 0.5 second, in assembly language? i am using a x86 processor, window NT, and the program compiled with turbo assembler 6.0. thanks. wtk :)

btw, i would like to know actually how many people out there are still learning assembly language. well, i mean *just* learning, not actually coding in assembly? i find asm is lot of fun. :) wtk

On the motorola processors, there are timer output compare registers which can be used to create a delay that is not clock speed-dependent. Basically you read in a clock, add a delay to its value, and set a timer output compare register to set a flag when the two are equal. You read this flag until it is set, then you can move on. You may need to wait until it is set and reset several times to get a .5sec delay. My guess is that intel has something similar. This method is reasonably complex and requires a basic understanding of the architecture...My guess is that you can probably find asm packages or something that have a subroutine that does this. To answer the "learning" question, Probably around 4-6 of my classes have dealt with assembly on some level, some very heavily, some only with respect to architecture design. Good luck, -SN

Delays are actually very important in logic components - they are common. You want a timing delay loop, but you don't want to calculate it according to your processor's clock speed. This is something like an EE would figure out (because obviously they are dealing with a specific system in a given state, not necessarily generic software). Instead, you have to use a timer - as was mentioned above. This thread explains a timer in x86 assembly.

If you were running under DOS instead of a protected mode OS, then there is a simple way to do a fixed timing loop that works for up to almost one second. The problem is that with protected mode OS's you can be interrupted out of any timing loop for long periods of time. The only way to do this is to make OS system API calls that return control back to you after the specified timeout. These are basic OS API function calls in windows used by VXD and Device drivers.

the following proc. will provide you with a delay of 10 micro-sec. ;;;;;;;;;;;;;;;;;;;;;;;;;;; DELAY proc near mov bx,64h w_1: mov cx,03e7h w_10: nop loop w_10 dec bx cmp bx,00h jne w_1 ret delay endp

As I've mentioned, I'm only familiar with the syntax of old school motorola assembly, but I'm guessing that the above loop makes two rather large assumptions: 1. That a NOP operation takes a certain amount of time...1 ns I think? This is clock-speed and processor dependent, so it's probably not a great assumption to make if accuracy is important. 2. That no interrupts will occur during the loop. Jack touched on this...Basically the OS can interrupt your program whenever it dang well feels like it and do its thing, then return control back to your program. So if you're just writing a loop of NOPs then there's no guarantee that you get exactly (or even close to) the right time delay. Use a timer. It's more complex, but it works. -SN