From:	silva AT dowco DOT com (Silva)
Newsgroups:	comp.lang.asm.x86,comp.lang.pascal.borland,comp.os.msdos.djgpp
Subject:	Re: How to align DOS memory block on page boundaries?
Date:	16 Aug 1998 19:07:30 GMT
Organization:	dowco.com internet (ISP)
Lines:	26
Approved:	<johnfine AT erols DOT com>
Message-ID:	<6r7ali$ob4$1@winter.news.erols.com>
References:	<6r6m7l$qbs$7 AT winter DOT news DOT erols DOT com>
NNTP-Posting-Host:	207-172-240-75.s12.as2.bsd.erols.com
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

"GiedriusS"  wrote:
>I want to allocate memory block (in DOS memory) which would be aligned
>on page boundaries, but I don't know how. Yeah, I need such memory
>block for DMA transfers.

Put a 256 scratch-pad in front of your buffer.

	page  60,132
	title 1K page buffer
code	segment
	assume	cs:code, ds:code, ss:code, es:code
	org	0100h		;DOS .COM starts here
start:	mov	dx,OFFSET DMApg ;point to a 1Kbyte page
	sub	dl,dl
;note: cs:dx "now" points at a 1K page
	mov	ax,4C00h	;exit to DOS with return(0)
	int	21h
	db	256   dup (?)	;spill-over
DMApg:	db	1000 dup (?)	;DMA page may start in spill-over
code	ends
	end	start

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