Re: A86: Terms
[Prev][Next][Index][Thread]
Re: A86: Terms
>Why can't there be more than one user interrupt installed at a time? On
>the pc when you install an interrupt, you just read in the vector of the
>int you want, set it to the start of your ISR (interrupt service routine),
>then call the old ISR at the end of yours. So if program A is running
>when you install your program B, program B reads in A's address, sets the
>vector (the address the cpu calls when that interrupt is run) to it's
>address (program B's address), then calls program A's address when it's
done.
Because the Z80 only supports three interrupt modes and all interrupts are
activated with hardware. Mode 0 puts data on a bus, Mode 1 resets to 38h 200
times per second, and mode 2 gets the data from a bus. It is all hardware
and that is how the Z80 was designed.
-Matt