Re: Real mode int from protected mode and back

"gerotica" <spamtrap@xxxxxxxxxx> wrote in message
news:548887fd-9256-42c2-8273-2daa41ae62ba@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Great... I can use the dos memory block to pass the parameters...
Can ES:EDI pointer to registers structure be null?

No, I've already said that. And anyway, how would you pass your R/M ISR its
parameters if you set it to null? ES:EDI must point to a DPMI Registers
structure in protected-mode memory. The values you set in the registers
structure are the values that the R/M registers will have when your R/M ISR
is invoked via the int 31h/0300h DPMI function.

And what do you mean by zeroing any unused registers? You mean zero
them all and then rewrite ax and dx (the needed registers) again?

Yes. This enusures you don't pass invalid segments in the segment registers,
or an invalid value in the "reserved" part of the registers structure. It's
the "safe" way to do it.

--
Jay

Jason Burgon - author of Graphic Vision
http://homepage.ntlworld.com/gvision

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