Re: [PARPORT] Scanner - Primax PagePartner

David Campbell (
Sat, 7 Feb 1998 15:09:20 +0000

> To: "Grant R. Guenther" <>
> Cc:,
> Subject: Re: [PARPORT] Scanner - Primax PagePartner
> Date: Fri, 06 Feb 1998 16:41:37 +0000
> From: Jonathan Buzzard <>

> said:
> > Capturing traces is an easy task if the parallel port device has a
> > DOS driver. We can run it under DOSemu and use some built-in
> > features of the emulator to capture traces of specific operations.
> > Unfortunately, most of these devices require Win95 - and won't work
> > in DOSemu. Of course, if you have a good logic analyser (capable of
> > capturing a trace of 24 channels at a sample rate of 10MHz for 20 or
> > 30 seconds) you could get a trace that way - but if you can afford
> > something like that, you'd buy the company rather than try to crack
> > their protocol ;-)
> Would it not be possible to write a lpt.vxd for Windows 95 that would
> allow a traces similar to those produced by DOSemu?


I'll research the VxD option for "feasability"...

What I have found so far is that some drivers simply "stun" the lpt.vxd
while they do what they need to (by direct access) and then wake it up
when they have finished. (Sounds very much like Linux ParPort to me).

If this is correct then we will require some method which can intercept
direct IO requests. Could someone correct me on this? Does DosEMU do
this by using a "virtual machine" (that is every asm command is
interpretted) and not executed by the CPU directly?

David Campbell
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