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/*
Fake86: A portable, open-source 8086 PC emulator.
Copyright (C)2010-2013 Mike Chambers
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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
/* i8237.c: functions to emulate the Intel 8237 DMA controller.
the Sound Blaster emulation functions rely on this! */
#include "config.h"
#include <stdint.h>
#include <stdio.h>
#include <memory.h>
#include "blaster.h"
#include "i8237.h"
extern struct blaster_s blaster;
struct dmachan_s dmachan[4];
uint8_t flipflop = 0;
extern void set_port_write_redirector (uint16_t startport, uint16_t endport, void *callback);
extern void set_port_read_redirector (uint16_t startport, uint16_t endport, void *callback);
extern uint8_t read86 (uint32_t addr32);
extern uint8_t RAM[0x100000];
uint8_t read8237 (uint8_t channel) {
uint8_t ret;
if (dmachan[channel].masked) return (128);
if (dmachan[channel].autoinit && (dmachan[channel].count > dmachan[channel].reload) ) dmachan[channel].count = 0;
if (dmachan[channel].count > dmachan[channel].reload) return (128);
//if (dmachan[channel].direction) ret = RAM[dmachan[channel].page + dmachan[channel].addr + dmachan[channel].count];
// else ret = RAM[dmachan[channel].page + dmachan[channel].addr - dmachan[channel].count];
if (dmachan[channel].direction == 0) ret = RAM[dmachan[channel].page + dmachan[channel].addr + dmachan[channel].count];
else ret = RAM[dmachan[channel].page + dmachan[channel].addr - dmachan[channel].count];
dmachan[channel].count++;
return (ret);
}
void out8237 (uint16_t addr, uint8_t value) {
uint8_t channel;
#ifdef DEBUG_DMA
printf ("out8237(0x%X, %X);\n", addr, value);
#endif
switch (addr) {
case 0x2: //channel 1 address register
if (flipflop == 1) dmachan[1].addr = (dmachan[1].addr & 0x00FF) | ( (uint32_t) value << 8);
else dmachan[1].addr = (dmachan[1].addr & 0xFF00) | value;
#ifdef DEBUG_DMA
if (flipflop == 1) printf ("[NOTICE] DMA channel 1 address register = %04X\n", dmachan[1].addr);
#endif
flipflop = ~flipflop & 1;
break;
case 0x3: //channel 1 count register
if (flipflop == 1) dmachan[1].reload = (dmachan[1].reload & 0x00FF) | ( (uint32_t) value << 8);
else dmachan[1].reload = (dmachan[1].reload & 0xFF00) | value;
if (flipflop == 1) {
if (dmachan[1].reload == 0) dmachan[1].reload = 65536;
dmachan[1].count = 0;
#ifdef DEBUG_DMA
printf ("[NOTICE] DMA channel 1 reload register = %04X\n", dmachan[1].reload);
#endif
}
flipflop = ~flipflop & 1;
break;
case 0xA: //write single mask register
channel = value & 3;
dmachan[channel].masked = (value >> 2) & 1;
#ifdef DEBUG_DMA
printf ("[NOTICE] DMA channel %u masking = %u\n", channel, dmachan[channel].masked);
#endif
break;
case 0xB: //write mode register
channel = value & 3;
dmachan[channel].direction = (value >> 5) & 1;
dmachan[channel].autoinit = (value >> 4) & 1;
dmachan[channel].writemode = (value >> 2) & 1; //not quite accurate
#ifdef DEBUG_DMA
printf ("[NOTICE] DMA channel %u write mode reg: direction = %u, autoinit = %u, write mode = %u\n",
channel, dmachan[channel].direction, dmachan[channel].autoinit, dmachan[channel].writemode);
#endif
break;
case 0xC: //clear byte pointer flip-flop
#ifdef DEBUG_DMA
printf ("[NOTICE] DMA cleared byte pointer flip-flop\n");
#endif
flipflop = 0;
break;
case 0x83: //DMA channel 1 page register
dmachan[1].page = (uint32_t) value << 16;
#ifdef DEBUG_DMA
printf ("[NOTICE] DMA channel 1 page base = %05X\n", dmachan[1].page);
#endif
break;
}
}
uint8_t in8237 (uint16_t addr) {
#ifdef DEBUG_DMA
printf ("in8237(0x%X);\n", addr);
#endif
switch (addr) {
case 3:
if (flipflop == 1) return(dmachan[1].reload >> 8);
else return(dmachan[1].reload);
flipflop = ~flipflop & 1;
break;
}
return (0);
}
void init8237() {
memset (dmachan, 0, sizeof (dmachan) );
set_port_write_redirector (0x00, 0x0F, &out8237);
set_port_read_redirector (0x00, 0x0F, &in8237);
set_port_write_redirector (0x80, 0x8F, &out8237);
set_port_read_redirector (0x80, 0x8F, &in8237);
}
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