re: Accessing memory with TNT

[Adam Barnes <amb@transtech.co.uk>]

>> I am using PharLap's TNT Extender trying to write some code
>> to access share memory on some network adapter board.
>> From the Base Address Register, looks like the board is
>> mapped to 0xF0000000.  Now, what system call in TNT (or other
>> ways) can I use to read and write this memory?
>> I've tried all these _dx_??? routines and still couldn't get
>> it to work.  May be I wasn't using them right.  One more
>> thing, I am using Microsoft Visual C 2.0.
>> Thank you
>> Henry Lau

Try the following at your own risk!
(Based largely on reading section 11.11
of the TNT DOS-Extender Reference Manual).

Compile with:
 cl /c filename.c
 386link @msvc32.dos filename.obj

/****************************************************************************/

#include <stdlib.h>
#include <stdio.h>
#include <pharlap.h>
#include <pldos32.h>

int map_phys( int phys_base, int size, int *lin_base )
{
	CONFIG_INF config ;
	UCHAR buf[256] ;
	int *p ;
	int mypages ;
	int mybase ;
	int err ;

	mybase = phys_base & 0xFFFFF000 ;
	mypages = ( size / 4096) ;
	if (mypages == 0)
		mypages = 1 ;
	_dx_config_inf(&config, buf) ;
	err = _dx_map_phys( config.c_ds_sel, mybase, mypages, (ULONG *)(&p) ) ;
	switch( err )
	{
		case 0:		break ;
		case 130:	printf( "_dx_map_phys: not supported in this DPMI\n" ) ;
				exit( 1 ) ;
		case 9:		printf( "_dx_map_phys: invalid segment selector\n" ) ;
				exit( 1 ) ;
		case 8:		printf( "_dx_map_phys: insufficient memory for page tables / -NOPAGE\n" ) ;
				exit( 1 ) ;
		default:	printf( "\n\n_dx_map_phys: unknown failure (0x%X)\n", err ) ;
				exit( 1 ) ;
	}
	*lin_base = ((phys_base - mybase) + (int)p ) ;
}

main()
{
	int *mem ;

	map_phys( 0xF0000000, 0x100000, (int *)&mem ) ;

	// mem[X] now corresponds (in this case) to the dword
	//  at offset X of the 1Mb region at 0xF0000000
	// (for 8-bit access declare variable 'mem' as a 'char *')
}

/****************************************************************************/

Adam Barnes
Transtech Parallel Systems
amb@transtech.co.uk
š
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