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From: gefuchs@wotan.uucp (Gill E. Fuchs)
Newsgroups: comp.sys.ibm.pc,comp.sys.intel
Subject: Re: 80286 protected mode programming
Keywords: 80286 protected mode
Message-ID: <1354@cmx.npac.syr.edu>
Date: 28 Mar 89 04:02:26 GMT
References: <86@necbsd.NEC.COM> <1455@mtunb.ATT.COM>
Sender: usenet@cmx.npac.syr.edu
Reply-To: gefuchs@top.cis.syr.edu (Gill E. Fuchs)
Organization: CIS Dept., Syracuse University
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>In article <86@necbsd.NEC.COM> sunshine@necbsd.NEC.COM (Roger Sunshine) writes:
>Does anyone have some sample code to switch the 80286 into protected mode
>and set up the segment descriptor tables?  ...

If you are using an AT type computer, you can enter into protected mode by
issuing BIOS interrupt 15, function 89 (both in hex).  You can also switch
back into real mode by issuing a command sequence to the CMOS clock and
keyboard controller (I think).  For more information on all BIOS interrupts,
a complete list is available in:
         IBM ROM BIOS, by Ray Duncan, published by MicroSoft Press,  $6.00.
Information on switching from protected into real mode, refer to:
         Switching Modes, PC Tech Journal, August 1985, p 163
Remember, this works only on IBM AT type machines.  If you want actual code,
it is available in Intel's 80286 Programmer's Reference Manual, though this
may be different than the code in the BIOS.

Gill Fuchs