Re: Interrupt modes

To: CALC-TI@LISTS.PPP.TI.COM
Subject: Re: Interrupt modes
From: Dave <dave@NOVANET.NET.AU>
Date: Wed, 13 Aug 1997 16:40:58 +1000
References: <3.0.1.16.19970811233853.2d4f1628@mail.tir.com>
Reply-To: Dave <dave@NOVANET.NET.AU>

Hi,

  After reading through my worn Z80 manual:

IM 0 - (default on Z80 reset):

An external device generates an IORQ, and then places an opcode on the
data bus
(eg. RST, CALL).  Not much use for programming.

IM 1:

On INT, branches to 0038h.  Effectively an NMI that can be masked.

IM 2:

On INT, external device places a 7-bit address on the data bus, this
address is appended
to the 8-bit I register.  The resulting address points to an entry in a
table of dwords
somewhere in memory - the dwords are the addresses of the int handlers.

Hope this helps.

        cya,
                Dave.

Thomas J. Hruska wrote:
>
> Quicky question about interrupt modes.  I've seen several programs that use
> IM 2.  So, what exactly is IM 0-2?  TIA
>
>                  Thomas J. Hruska -- thruska@tir.com
> Shining Light Productions -- "Meeting the needs of fellow programmers"
>          http://www.geocities.com/SiliconValley/Heights/8504
>                     http://shinelight.home.ml.org

References:

Interrupt modes

From: "Thomas J. Hruska" <thruska@TIR.COM>