Date: Wed, 12 Aug 1998 12:04:53 +0300 (IDT)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: Michel Gallant <mgallant AT grassroots DOT ns DOT ca>
cc: djgpp AT delorie DOT com
Subject: Re: Detecting interrupt on printer port 
In-Reply-To: <C22A1.62$Qi3.325552@sapphire.mtt.net> 
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On Tue, 11 Aug 1998, Michel Gallant wrote:

> It also sets a printer control register (bit 4 on port 890) which
> apparently is needed to enable interrups on ACK (according to HELPPC,
> a technical help database by David Jurgens).  However, the counter
> (supposed to increment on every interrupt) stays at zero!

Did you make sure that the LPT1 interface is actually set (by a DIP 
switch or a jumper on the motherboard) to generate an interrupt?  My 
references indicate that this is sometimes required.

Also, Ralf Brown's Interrupt List says something to the effect that most 
adapters don't reliably generate Int 0Fh.

As yet another hint, I think the interrupt is only generated after you 
write a character to the printer.  But your code never writes anything to 
the printer, or so it seems.