66 lines
1.6 KiB
HTML
66 lines
1.6 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type"
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content="text-html; charset=Windows-1252">
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<title>INT 8 - System timer</title>
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<meta name="FORMATTER" content="Microsoft FrontPage 2.0">
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</head>
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<body>
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<h1><a name="kap_interrupt_0050"></a>INT 8 - System timer</h1>
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<p> no input data</p>
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<p> % related memory:</p>
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<p> 40:6C = Daily timer counter (4 bytes)</p>
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<p> 40:70 = 24 hr overflow flag (1 byte)</p>
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<p> 40:67 = Day counter on all products after AT</p>
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<p> 40:40 = Motor shutoff counter - decremented until 0 then</p>
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<p> shuts off diskette motor</p>
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<p> - ~INT 1C~ is invoked as a user interrupt</p>
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<p> - the byte at 40:70 is a flag that certain DOS functions use</p>
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<p> and adjust the date if necessary. Since this is a flag and</p>
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<p> not a counter it results in DOS (not the ~RTC~) losing days</p>
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<p> when several midnights pass before a DOS call</p>
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<p> - generated 18.2 times per second by the ~8253~ Programmable
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Interval</p>
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<p> Timer (PIT)</p>
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<p> - normal INT 8 execution takes approximately 100 microseconds</p>
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<p> - see ~8253~</p>
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<hr>
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<table border="0" width="100%" cols="3">
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<tr>
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<td width="33%">Zurück zum <a href="inte1at0.htm">Interrupt
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Info</a>. </td>
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<td align="center" width="33%"><a
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href="mailto:Roger.Morgan@htl-steyr.ac.at">Roger Morgan</a>
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/ 1998 </td>
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<td align="right" width="33%"><font size="1">L.Änderung <!--webbot
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bot="Timestamp" s-type="EDITED" s-format="%d.%m.%y"
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startspan -->29.03.99<!--webbot bot="Timestamp" endspan
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i-checksum="13964" --> </font></td>
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</tr>
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</table>
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</body>
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</html>
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