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Serial Interrupts failed??

Serial Interrupts failed??

Serial Interrupts failed??

I am having some problems with my serial port file transfer program. This program uses the serial port interrupts. Can anyone tell me why the following code will fail to have any serial port interrupts coming in?

a: mov ah, 6
   mov dl, 0ffh
   int 21h
   jnz b
   jmp a

b: ...test for ESC key ....

This is the loop that my program goes through when waiting for serial interrupts. It tests the keyboard for ESC keypress.

However, the following code works:

a: mov ah, 1
   int 16h
   jnz b
   jmp a

b: ....test for ESC key ....

Why does one works while the other fails? Both seems to do a software INT very fast.

Thanks a lot.

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