Timer in Assembler

Question

assembler

Greetings.

At the university, they set a coursework, the task is as follows:

Read the current time, add a specified interval to it (for example, 5 seconds) and set an alarm for the received time.

I started writing, diligently studying codenet.ru, DOSBox and TASM. It turned out the following: pastebin.com/XxNbhBT6 In order to work with the timer, I use the 1Ah interrupt. Function 02h I read the current time, then add 5 seconds and set the timer with function 06h. This is where the main difficulty awaited me. The documentation on codenet.ru says:

06H - set the real-time clock signal. At the specified time, the user program is called on the interrupt vector INT 4aH.

Googling a little, I found out that interrupt interception is defined as follows:

lea dx, some_function
mov ah,25h
mov al,4Ah


Created a function that should output a string on a timer signal. But when the resulting exe-shnik is launched in dosbox, the following situation occurs: messages about reading the time and the timer are displayed simultaneously (that is, 5 seconds does not pass). After that the program hangs and it is necessary to kill together with dosbox'om.

Answer 1

Are you sure you are calling int 21h
after lea dx, some_function
mov ah,25h
mov al,4Ah ?