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From: bmarsh@cod.NOSC.MIL (William C. Marsh)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Mice
Keywords: mouse protocols
Message-ID: <2445@cod.NOSC.MIL>
Date: 7 Nov 90 21:28:11 GMT
References: <2410@wn1.sci.kun.nl> <2361@moscom.UUCP>
Reply-To: bmarsh@cod.nosc.mil.UUCP (William C. Marsh)
Distribution: comp
Organization: Naval Ocean Systems Center, San Diego
Lines: 22

In article <2361@moscom.UUCP> wjb@moscom.UUCP (Bill de Beaubien) writes:
>In article <2410@wn1.sci.kun.nl> ge@wn3.sci.kun.nl (Ge' Weijers) writes:
>>Does anyone have the protocol specifications of the Microsoft serial mouse
>>available, especially how do you know one is connected.

>The easiest way to see if a mouse is connected is to use int 33h, service 0.
>Load AX with 0, call int 33h.  If AX=0FFFFh, mouse support is available,
>and BX contains the number of buttons.  If AX is unchanged, no mouse support
>is available.

First, check to make sure the interrupt vector used by the 'int 33h' is not
all zeros!  Older versions of DOS did not initialize all the interrupt vectors
to point to an iret, so simply calling the interrupt would result in a crash.

This is important for looking for an EMS driver too.

Bill
-- 
Bill Marsh, Naval Ocean Systems Center, San Diego, CA
{arpa,mil}net: bmarsh@cod.nosc.mil
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"If you are not part of the solution, you're part of the problem..."