DOS 7.1 programming for Intel EP80579

[MichaelW]

1) Switch into protected mode, setup a segment register, and switch back

Will someone provide me sample of this option? I searched on net, i got few samples but they are confusing? also none of them worked well.
I would like to set GS or FS segment register with base address 0 & segment limit of 4GB.

I provided a link to a simple example in my first post in this thread.

[suryakant]

Thanks all,

when my application runs, its in real mode (but not in virtual 8086 mode).

Following is the dump of EFLAGS: 00007202 h  &  CR0 : 00000011h

I used following code to display these values. Now how to go ahead?

            pushfd
            pop eax
            mov DisplayValue, eax      ; Value to be displayed
            call displayLong            

            mov eax, cr0
            mov DisplayValue, eax      ; Value to be displayed
            call displayLong            

[suryakant]

I provided a link to a simple example in my first post in this thread.

I used the same code, but when LGDT instruction is executed, processor hangs.

[MichaelW]

I used the same code, but when LGDT instruction is executed, processor hangs.

Did you try the EXE that I provided?

[suryakant]

I used the same code, but when LGDT instruction is executed, processor hangs.

Did you try the EXE that I provided?

Yes,  It displays following and hangs. (pressing key has no effect, does not return to dos prompt)

EAD404920231312F32332F303900FC00
1
1

[MichaelW]

Are you running this on the EP80579, or some other system? It looks like the A20 address line is already enabled, so try eliminating the call to EnableA20_PS2 and see if that helps. HIMEM.SYS had approximately 20 A20 address line handlers to cover the variety of hardware available at the time. I provided only one, that I'm guessing uses the most common method today, but I don't actually know this.

[suryakant]

Thanks Micheal, thanks all.

In Config.sys  dos was loaded in high memory, also HIGHMEM.SYS and EMM386.SYS were loaded. I removed them

Now application runs in real mode first, switches successfully to protected mode and comes back...

Thanks again Micheal for providing code with exe.

Now i ll concentrate on my main application code... I ll update as I move ahead..  :bg

[clive]

Also I need to write application software in C. Visual Studio 2008 does not seem to support dos function calls in C... also I could not get proper switches to compile program for 16 bit OS. Shall I go for Turbo C for DOS for application programming and MASM in Visual Studio for Device drivers? Will I need to do some changes?

Back when I did this kind of stuff and did C and assembler in 32-bit under DOS, I'd use Watcom and a DOS-Extender (DOS4GW, PMW, Causeway, DOS32A). You could pretty much do all the driver and interrupt stuff within a "monolithic" application. The Watcom compiler/linker could generate 32-bit applications for a lot of platforms, pulled 32-bit objects built with MASM. It was also easy enough to write code to load and bind Win32 drivers, EXE and DLLs. I was doing magnetic tape, CD/DVD burning, and 802.11 PCI/PCMCIA wireless, but applications like Ghost and DriveImage used similar methods to deliver platform agnostic DOS 32-bit solutions. Pretty much all my Win32 console apps (using stdio/stdlib) can be built for DOS by simply recompiling.

For 16-bit stuff Microsoft C (5.x, 6.0, 7.0, 8.0 [MSVC 1.52c]), MASM (5.x, 6.xx) worked well, Turbo C 2.x or 3.x or TASM would all be quite workable too. I think Watcom would do 16-bit too, but I always used it for 32-bit.

If you're running on anything 386 or beyond, doing much 16-bit coding seems like an unnecessary exercise.

-Clive

[suryakant]

Hi all,

I have successfully written test code to transmit & receive one byte on CAN...   :bg
Now its time to go for full fledged driver... Hope you people are there for me  :bg

Thanks friends,,,  :U