Path: utzoo!attcan!uunet!aplcen!haven!adm!news
From: CDCKAB%EMUVM1.BITNET@cunyvm.cuny.edu ( Karl Brendel)
Newsgroups: comp.lang.pascal
Subject: (R)Text Device Drivers in TP
Message-ID: <24696@adm.BRL.MIL>
Date: 5 Oct 90 12:50:31 GMT
Sender: news@adm.BRL.MIL
Lines: 42


In article <37915@ut-emx.uucp>, Carl Seiler <seiler@walt.cc.utexas.edu>
writes:

>Has anyone had any luck with the Turbo Pascal unit which is listed on
>page 225 in the 5.0 Reference guide and 365 of the 4.0 book, and
>probably included in 5.5 somewhere as well.  It is an example of a
>text file device driver for the IBM PC.  When run with the short
>program which follows, my system stops.

I have not used the routine and don't care to type it in and try it, but
perhaps my remarks will not be without value:

The unit in question is full of opportunities for mistyped instructions
to compile fine but cause problems later: Other than checking for
syntax, the compiler does nothing much to validate inline code, so first
triple-check the code you typed against the source _and_ the read.me
files (in the event of a manual error which was corrected there).

Given the point at which the error occurs, tho, I'm inclined to suspect
that the real problem is either that the com port has not been
initialized or else there is a hardware conflict. Asynch communication
was perhaps not a good choice for a TFDD example because of the
additional issues raised. Note that the example program uses this unit
to assign a TFDD to COM1 with specific parameters. If another device is
already using COM1 (or the associated IRQ) or if COM1 is not set to the
same parameters, you can expect some problem with this code. Try the
example program on a port known to be free of conflicts, and use the DOS
MODE command to initialize the port to the same parameters used in the
example.

If these remarks don't help, then I leave you to the advice of others,
because we have nearly exhausted my knowledge of asynch programming. :)

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