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Diffstat (limited to 'src/fake86/i8237.c')
| -rwxr-xr-x | src/fake86/i8237.c | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/src/fake86/i8237.c b/src/fake86/i8237.c new file mode 100755 index 0000000..2ad9498 --- /dev/null +++ b/src/fake86/i8237.c @@ -0,0 +1,133 @@ +/* + 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); +} |