ref: 4c510b80e7330e4cb77b1b564483f1b5c3a2dd0f
dir: /Game/src/audiolib/dma.c/
/*
Copyright (C) 1994-1995 Apogee Software, Ltd.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
/**********************************************************************
module: DMA.C
author: James R. Dose
date: February 4, 1994
Low level routines to for programming the DMA controller for 8 bit
and 16 bit transfers.
(c) Copyright 1994 James R. Dose. All Rights Reserved.
**********************************************************************/
#include <dos.h>
#include <conio.h>
#include <stdlib.h>
#include "dma.h"
#define DMA_MaxChannel 7
#define VALID ( 1 == 1 )
#define INVALID ( !VALID )
#define BYTE 0
#define WORD 1
typedef struct
{
int Valid;
int Width;
int Mask;
int Mode;
int Clear;
int Page;
int Address;
int Length;
} DMA_PORT;
static const DMA_PORT DMA_PortInfo[ DMA_MaxChannel + 1 ] =
{
{ VALID, BYTE, 0xA, 0xB, 0xC, 0x87, 0x0, 0x1 },
{ VALID, BYTE, 0xA, 0xB, 0xC, 0x83, 0x2, 0x3 },
{ INVALID, BYTE, 0xA, 0xB, 0xC, 0x81, 0x4, 0x5 },
{ VALID, BYTE, 0xA, 0xB, 0xC, 0x82, 0x6, 0x7 },
{ INVALID, WORD, 0xD4, 0xD6, 0xD8, 0x8F, 0xC0, 0xC2 },
{ VALID, WORD, 0xD4, 0xD6, 0xD8, 0x8B, 0xC4, 0xC6 },
{ VALID, WORD, 0xD4, 0xD6, 0xD8, 0x89, 0xC8, 0xCA },
{ VALID, WORD, 0xD4, 0xD6, 0xD8, 0x8A, 0xCC, 0xCE },
};
int DMA_ErrorCode = DMA_Ok;
#define DMA_SetErrorCode( status ) \
DMA_ErrorCode = ( status );
/*---------------------------------------------------------------------
Function: DMA_ErrorString
Returns a pointer to the error message associated with an error
number. A -1 returns a pointer the current error.
---------------------------------------------------------------------*/
char *DMA_ErrorString
(
int ErrorNumber
)
{
char *ErrorString;
switch( ErrorNumber )
{
case DMA_Error :
ErrorString = DMA_ErrorString( DMA_ErrorCode );
break;
case DMA_Ok :
ErrorString = "DMA channel ok.";
break;
case DMA_ChannelOutOfRange :
ErrorString = "DMA channel out of valid range.";
break;
case DMA_InvalidChannel :
ErrorString = "Unsupported DMA channel.";
break;
default :
ErrorString = "Unknown DMA error code.";
break;
}
return( ErrorString );
}
/*---------------------------------------------------------------------
Function: DMA_VerifyChannel
Verifies whether a DMA channel is available to transfer data.
---------------------------------------------------------------------*/
int DMA_VerifyChannel
(
int channel
)
{
int status;
int Error;
status = DMA_Ok;
Error = DMA_Ok;
if ( ( channel < 0 ) || ( DMA_MaxChannel < channel ) )
{
Error = DMA_ChannelOutOfRange;
status = DMA_Error;
}
else if ( DMA_PortInfo[ channel ].Valid == INVALID )
{
Error = DMA_InvalidChannel;
status = DMA_Error;
}
DMA_SetErrorCode( Error );
return( status );
}
/*---------------------------------------------------------------------
Function: DMA_SetupTransfer
Programs the specified DMA channel to transfer data.
---------------------------------------------------------------------*/
int DMA_SetupTransfer
(
int channel,
char *address,
int length,
int mode
)
{
DMA_PORT *Port;
int addr;
int ChannelSelect;
int Page;
int HiByte;
int LoByte;
int TransferLength;
int status;
status = DMA_VerifyChannel( channel );
if ( status == DMA_Ok )
{
Port = &DMA_PortInfo[ channel ];
ChannelSelect = channel & 0x3;
addr = ( int )address;
if ( Port->Width == WORD )
{
Page = ( addr >> 16 ) & 255;
HiByte = ( addr >> 9 ) & 255;
LoByte = ( addr >> 1 ) & 255;
// Convert the length in bytes to the length in words
TransferLength = ( length + 1 ) >> 1;
// The length is always one less the number of bytes or words
// that we're going to send
TransferLength--;
}
else
{
Page = ( addr >> 16 ) & 255;
HiByte = ( addr >> 8 ) & 255;
LoByte = addr & 255;
// The length is always one less the number of bytes or words
// that we're going to send
TransferLength = length - 1;
}
// Mask off DMA channel
outp( Port->Mask, 4 | ChannelSelect );
// Clear flip-flop to lower byte with any data
outp( Port->Clear, 0 );
// Set DMA mode
switch( mode )
{
case DMA_SingleShotRead :
outp( Port->Mode, 0x48 | ChannelSelect );
break;
case DMA_SingleShotWrite :
outp( Port->Mode, 0x44 | ChannelSelect );
break;
case DMA_AutoInitRead :
outp( Port->Mode, 0x58 | ChannelSelect );
break;
case DMA_AutoInitWrite :
outp( Port->Mode, 0x54 | ChannelSelect );
break;
}
// Send address
outp( Port->Address, LoByte );
outp( Port->Address, HiByte );
// Send page
outp( Port->Page, Page );
// Send length
outp( Port->Length, TransferLength );
outp( Port->Length, TransferLength >> 8 );
// enable DMA channel
outp( Port->Mask, ChannelSelect );
}
return( status );
}
/*---------------------------------------------------------------------
Function: DMA_EndTransfer
Ends use of the specified DMA channel.
---------------------------------------------------------------------*/
int DMA_EndTransfer
(
int channel
)
{
DMA_PORT *Port;
int ChannelSelect;
int status;
status = DMA_VerifyChannel( channel );
if ( status == DMA_Ok )
{
Port = &DMA_PortInfo[ channel ];
ChannelSelect = channel & 0x3;
// Mask off DMA channel
outp( Port->Mask, 4 | ChannelSelect );
// Clear flip-flop to lower byte with any data
outp( Port->Clear, 0 );
}
return( status );
}
/*---------------------------------------------------------------------
Function: DMA_GetCurrentPos
Returns the position of the specified DMA transfer.
---------------------------------------------------------------------*/
char *DMA_GetCurrentPos
(
int channel
)
{
DMA_PORT *Port;
unsigned long addr;
int status;
addr = NULL;
status = DMA_VerifyChannel( channel );
if ( status == DMA_Ok )
{
Port = &DMA_PortInfo[ channel ];
if ( Port->Width == WORD )
{
// Get address
addr = inp( Port->Address ) << 1;
addr |= inp( Port->Address ) << 9;
// Get page
addr |= inp( Port->Page ) << 16;
}
else
{
// Get address
addr = inp( Port->Address );
addr |= inp( Port->Address ) << 8;
// Get page
addr |= inp( Port->Page ) << 16;
}
}
return( ( char * )addr );
}
/*---------------------------------------------------------------------
Function: DMA_GetTransferCount
Returns how many bytes are left in the DMA's transfer.
---------------------------------------------------------------------*/
int DMA_GetTransferCount
(
int channel
)
{
DMA_PORT *Port;
int count;
int status;
status = DMA_Ok;
count = 0;
if ( ( channel < 0 ) || ( DMA_MaxChannel < channel ) )
{
status = DMA_ChannelOutOfRange;
}
else if ( DMA_PortInfo[ channel ].Valid == INVALID )
{
status = DMA_InvalidChannel;
}
if ( status == DMA_Ok )
{
Port = &DMA_PortInfo[ channel ];
outp( Port->Clear, 0 );
count = inp( Port->Length );
count += inp( Port->Length ) << 8;
if ( Port->Width == WORD )
{
count <<= 1;
}
}
DMA_SetErrorCode( status );
return( count );
}