ref: 8680acdefff5d3ff4190431884eed585a9da6294
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 ); }