implement FX33

Changelog.md

@@ -1,6 +1,7 @@
 # Changelog
 
 ## 2024-04-27
+- Implement FX33 - BCD
 - Implement 2NNN - CALL addr
 - Fixes issues for printing IBM logo
 - Framebuffer is now part of the chip8

Readme.md

@@ -3,7 +3,7 @@
 ## What?
 - Another *chip8* emulator in rust
 - Only instructions used to display IBM logo are implemented
-- Next to implement for pong is `0xfe33`
+- Next to implement for pong is `fX65`
 - To run it: `cargo run --bin emulator chip8-roms/IBM_logo.ch8`
 - To debug prepend `RUST_LOG=debug`
 - [Changelog](https://github.com/gthvn1/chip8-emulator/blob/master/Changelog.md)

src/chip8.rs

@@ -269,7 +269,16 @@ impl Chip8 {
                 self.mem[DISPLAY_OFFSET..(DISPLAY_OFFSET + DISPLAY_SIZE)].copy_from_slice(&fb_copy);
             }
             0xE => return Err(Chip8Error::NotImplemented(opcode)),
-            0xF => return Err(Chip8Error::NotImplemented(opcode)),
+            0xF => match opcode.nn() {
+                0x33 => {
+                    let vx = self.vregs[opcode.x() as usize];
+                    let idx = self.i as usize;
+                    self.mem[idx] = ((vx / 100) % 10) as u8; // hundreds digit
+                    self.mem[idx + 1] = ((vx / 10) % 10) as u8; // tens digit
+                    self.mem[idx + 2] = (vx % 10) as u8; // ones digit
+                }
+                _ => return Err(Chip8Error::NotImplemented(opcode)),
+            },
             _ => {
                 return Err(Chip8Error::UnknownOpcode(opcode));
             }