[ram] Normalize memory access across memory devices

src/emu/mmu.rs

@@ -1,5 +1,5 @@
 use crate::emu::iomem::MemoryMappedIO;
-use crate::emu::mem::RamMemory;
+use crate::emu::ram::RamMemory;
 use crate::misc::emulator_error::DeviceType::MMU;
 
 use crate::misc::emulator_error::EmulatorError::UnreachableMemory;
@@ -42,7 +42,8 @@ impl Memory for MappedMemory {
                 self.memory_mapped_io.try_get_byte(address)
             }
             RAM_MEM_START..=RAM_MEM_END => {
-                self.ram_memory.try_get_byte(address)
+                let memory_index = address - RAM_MEM_START;
+                self.ram_memory.try_get_byte(memory_index)
             }
             _ => { Err(UnreachableMemory(MMU, address)) }
         }?;

src/emu/mod.rs

@@ -1,4 +1,4 @@
 pub mod cpu;
 pub mod mmu;
-pub mod mem;
+pub mod ram;
 pub mod iomem;

src/emu/ram.rs

@@ -4,7 +4,8 @@ use crate::misc::emulator_error::DeviceType::RAM;
 use crate::misc::emulator_error::EmulatorError;
 use crate::misc::result::EmulatorResult;
 
-const MEM_LENGTH: usize = 2 << 24;
+const MAPPED_MEMORY_NOT_REQUIRED: u8 = 8;
+const MEM_LENGTH: usize = (2 << 24) - (MAPPED_MEMORY_NOT_REQUIRED as usize);
 
 #[derive(Clone, Debug)]
 pub struct RamMemory {
@@ -45,7 +46,7 @@ impl Memory for RamMemory {
 
 #[cfg(test)]
 mod tests{
-    use crate::emu::mem::RamMemory;
+    use crate::emu::ram::RamMemory;
     use crate::emu::mmu::Memory;
     const EXAMPLE_ADDRESS:u32=0x24;