[mem] Add mapped memory

src/emu/iomem.rs

@@ -0,0 +1,60 @@
+
+use crate::emu::mmu::Memory;
+
+#[derive(Debug, Copy, Clone)]
+pub struct MemoryMappedIO {
+    keyboard_bits: [u8;2],
+    program_counter: [u8; 3],
+    pixel_reg: u8,
+    audio_sample_address_base: [u8; 2],
+}
+
+impl MemoryMappedIO {
+    pub fn new() -> MemoryMappedIO {
+        MemoryMappedIO {
+            keyboard_bits: [0,0],
+            program_counter: [0, 0, 0],
+            pixel_reg: 0,
+            audio_sample_address_base: [0, 0],
+        }
+    }
+}
+
+const KEYBOARD_BIT_START: u32 = 0;
+const KEYBOARD_BIT_END: u32 = 1;
+const PC_START_ADDR: u32 = 2;
+const PC_LEN: u32 = 3;
+const PC_END_ADDR: u32 = PC_START_ADDR + PC_LEN - 1;
+
+const PIXEL_BASE: u32 = 5;
+const AUDIO_SAMPLE_BASE_START: u32 = 6;
+const AUDIO_SAMPLE_BASE_LEN: u32 = 2;
+const AUDIO_SAMPLE_BASE_END: u32 = AUDIO_SAMPLE_BASE_START + AUDIO_SAMPLE_BASE_LEN - 1;
+
+impl Memory for MemoryMappedIO {
+    fn get_byte(&self, address: u32) -> u8 {
+        match address {
+            KEYBOARD_BIT_START..=KEYBOARD_BIT_END => {
+                let addr_usize = address as usize;
+                log::trace!("Fetching keyboard bits segment {}",addr_usize);
+                self.keyboard_bits[addr_usize]
+            },
+            PC_START_ADDR..=PC_END_ADDR => {
+                let pc_index = (address - PC_START_ADDR) as usize;
+                log::trace!("Fetching PC {:?} bit segment {}",self.program_counter,pc_index);
+                self.program_counter[pc_index]
+            },
+            PIXEL_BASE => {
+                log::trace!("Fetching pixel base reg {}",self.pixel_reg);
+                self.pixel_reg
+            },
+            AUDIO_SAMPLE_BASE_START => self.audio_sample_address_base[0],
+            AUDIO_SAMPLE_BASE_END => self.audio_sample_address_base[1],
+            _ => { panic!("Unreachable code") }
+        }
+    }
+
+    fn set_byte(&mut self, address: u32, val: u8) {
+        todo!()
+    }
+}