The dos print spooler polls the parallel port on the timer interrupt, no
interrupt from the printer is needed

-timer interrupt jumps to hooked service routine (about 18 times a second)
-printer status check
-if printer buffer empty send new characters
-if printing done unhook timer interrupt
-jump to original timer service routine
-original timer service routine returns controll to dos till next timer
interrupt

Peter pvh@vertonet.com


-----Original Message-----
From: Sean Breheny <shb7@CORNELL.EDU>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Tuesday, May 18, 1999 8:42 PM
Subject: Re: Multitasking without interrupt ?


>Hi Imre,
>
>How does it work on PC's without a printer IRQ? I thought I had used it on
>ones that probably didn't have a printer interrupt.
>
>Sean
>
>At 11:32 AM 5/17/99 +0200, you wrote:
>>Hi,
>>only as a small remark: the DOS print spooler (I do not know whether
>>another ones...) is working on an interrupt basis, as the printer tells
>>with an IT if the data has been printed, so asks for new data. There is no
>>time slicing.
>>Imre
>>
>>
>
>|
>| Sean Breheny
>| Amateur Radio Callsign: KA3YXM
>| Electrical Engineering Student
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