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fox32+fox32rom: Use DMA for the disk controller

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Instead of accessing one byte at a time, use a DMA-like system to
read/write a whole sector at a time directly to/from memory.
This commit is contained in:
Ry 2022-03-12 13:12:10 -08:00
parent 998646cb80
commit 93d331bb07
2 changed files with 16 additions and 20 deletions
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22
src/bus.rs
View File

@ -88,11 +88,8 @@ impl Bus {
}
}
0x20 => {
// we're reading from the sector buffer
if address_or_id > 512 {
panic!("attempted to read past the end of the disk controller sector buffer");
}
self.disk_controller.sector_buffer[address_or_id] as u32
// we're getting the location of the memory sector buffer
self.disk_controller.buffer_pointer as u32
}
_ => panic!("invalid disk controller port"),
}
@ -174,27 +171,24 @@ impl Bus {
};
}
0x20 => {
// we're writing to the sector buffer
if address_or_id > 512 {
panic!("attempted to read past the end of the disk controller sector buffer");
}
self.disk_controller.sector_buffer[address_or_id] = word as u8;
// we're setting the location of the memory sector buffer
self.disk_controller.buffer_pointer = word as usize;
}
0x30 => {
// we're reading the specified sector of the specified disk id into the sector buffer
// we're reading the specified sector of the specified disk id into the memory sector buffer
if address_or_id > 3 {
panic!("invalid disk ID");
}
self.disk_controller.set_current_sector(address_or_id as u8, word);
self.disk_controller.read_into_buffer(address_or_id as u8);
self.disk_controller.read_into_memory(address_or_id as u8, self.memory.ram());
}
0x40 => {
// we're writing the specified sector to the specified disk id from the sector buffer
// we're writing the specified sector to the specified disk id from the memory sector buffer
if address_or_id > 3 {
panic!("invalid disk ID");
}
self.disk_controller.set_current_sector(address_or_id as u8, word);
self.disk_controller.write_from_buffer(address_or_id as u8);
self.disk_controller.write_from_memory(address_or_id as u8, self.memory.ram());
}
_ => panic!("invalid disk controller port"),
}

14
src/disk.rs
View File

@ -1,5 +1,7 @@
// disk.rs
use crate::memory::MemoryRam;
use std::fs::File;
use std::io::{Seek, SeekFrom, Read, Write};
use rfd::FileDialog;
@ -22,14 +24,14 @@ impl Disk {
pub struct DiskController {
pub disk: [Option<Disk>; 4],
pub sector_buffer: [u8; 512],
pub buffer_pointer: usize,
}
impl DiskController {
pub fn new() -> Self {
DiskController {
disk: [None, None, None, None],
sector_buffer: [0; 512]
buffer_pointer: 0x00000000
}
}
pub fn select_file(&self) -> Option<File> {
@ -64,18 +66,18 @@ impl DiskController {
let disk = self.disk[disk_id as usize].as_mut().expect("attempted to access unmounted disk");
disk.current_sector
}
pub fn read_into_buffer(&mut self, disk_id: u8) -> usize {
pub fn read_into_memory(&mut self, disk_id: u8, ram: &mut MemoryRam) -> usize {
let disk = self.disk[disk_id as usize].as_mut().expect("attempted to access unmounted disk");
let mut temp_buffer = [0u8; 512];
let number_of_bytes_read = disk.file.read(&mut temp_buffer).unwrap();
self.sector_buffer = temp_buffer;
ram[self.buffer_pointer..self.buffer_pointer+512].copy_from_slice(&temp_buffer);
number_of_bytes_read
}
pub fn write_from_buffer(&mut self, disk_id: u8) -> usize {
pub fn write_from_memory(&mut self, disk_id: u8, ram: &MemoryRam) -> usize {
let disk = self.disk[disk_id as usize].as_mut().expect("attempted to access unmounted disk");
let number_of_bytes_written = disk.file.write(&mut self.sector_buffer).unwrap();
let number_of_bytes_written = disk.file.write(ram.get(self.buffer_pointer..self.buffer_pointer+512).unwrap()).unwrap();
number_of_bytes_written
}
}