75 lines
2.4 KiB
Rust
75 lines
2.4 KiB
Rust
use crate::emu::mmu::Memory;
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use crate::misc::emulator_error::EmulatorError;
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use crate::misc::endian::MemoryOperations;
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use crate::misc::result::EmulatorResult;
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#[derive(Debug, Copy, Clone)]
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pub struct MemoryMappedIO {
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//FIXME use a keyboard
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keyboard_bytes: [u8; 2],
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program_counter: [u8; 3],
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//FIXME use a device
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pixel_reg: u8,
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//FIXME use a device
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audio_sample_address_base: [u8; 2],
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}
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impl MemoryMappedIO {
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pub fn new() -> MemoryMappedIO {
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MemoryMappedIO {
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keyboard_bytes: [0, 0],
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program_counter: [0, 0, 0],
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pixel_reg: 0,
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audio_sample_address_base: [0, 0],
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}
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}
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}
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// 2 byte keyboard bits
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const KEYBOARD_BIT_START: u32 = 0;
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const KEYBOARD_BIT_END: u32 = 1;
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// 3 bytes PC
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const PC_START_ADDR: u32 = 2;
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const PC_LEN: u32 = 3;
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const PC_END_ADDR: u32 = PC_START_ADDR + PC_LEN - 1;
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// 1 byte pixel base reg
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const PIXEL_BASE: u32 = 5;
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// 2 byte audio sample base reg
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const AUDIO_SAMPLE_BASE_START: u32 = 6;
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const AUDIO_SAMPLE_BASE_LEN: u32 = 2;
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const AUDIO_SAMPLE_BASE_END: u32 = AUDIO_SAMPLE_BASE_START + AUDIO_SAMPLE_BASE_LEN - 1;
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impl Memory for MemoryMappedIO {
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fn try_get_byte(&self, address: u32) -> EmulatorResult<u8> {
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let byte = match address {
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KEYBOARD_BIT_START..=KEYBOARD_BIT_END => {
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let addr_usize = address as usize;
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let keyboard_byte = self.keyboard_bytes[addr_usize];
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log::trace!("Fetching keyboard({}) byte segment {} -> {}",MemoryOperations::read_big_endian_u16(&self.keyboard_bytes),address,keyboard_byte);
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keyboard_byte
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}
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PC_START_ADDR..=PC_END_ADDR => {
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let pc_index = (address - PC_START_ADDR) as usize;
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let pc_byte = self.program_counter[pc_index];
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log::trace!("Fetching PC({}) byte segment {} -> {}",MemoryOperations::read_big_endian_u24(&self.program_counter),pc_index,pc_byte);
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pc_byte
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}
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PIXEL_BASE => {
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log::trace!("Fetching pixel base reg {}",self.pixel_reg);
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self.pixel_reg
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}
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AUDIO_SAMPLE_BASE_START => self.audio_sample_address_base[0],
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AUDIO_SAMPLE_BASE_END => self.audio_sample_address_base[1],
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_ => { panic!("Unreachable code") }
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};
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Ok(byte)
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}
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fn try_set_byte(&mut self, address: u32, val: u8) -> EmulatorResult<()> {
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todo!()
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}
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}
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