more coverage

gemma/src/chip8/computer.rs

@@ -91,7 +91,7 @@ impl Chip8Computer {
     }
 
     pub fn step_system(&mut self) -> &mut Chip8Computer {
-        debug!("Stepping System 1 Step");
+        println!("Stepping System 1 Step");
         // read the next instruction
         let local_memory = &self.memory;
 
@@ -107,6 +107,7 @@ impl Chip8Computer {
 
         match self.state {
             Chip8CpuStates::WaitingForInstruction => {
+                println!("Ticking sound, delay, video");
                 self.sound_timer.tick();
                 self.delay_timer.tick();
                 self.video_memory.tick();

gemma/src/chip8/instructions.rs

@@ -884,9 +884,6 @@ impl Chip8CpuInstructions {
                     value_to_poke = (y_register - x_register) as u16;
                     1
                 };
-
-                debug!("SUB CARRY -> REGISTER 1 = [0x{x:02x}] / [{x_register}] REGISTER 2 = [0x{y:02x}] / [{y_register}] SUB = {value_to_poke} CARRY = {new_value}");
-
                 input.registers.poke(*x, value_to_poke as u8);
                 input.registers.poke(0xf, new_value);
             }
@@ -938,8 +935,11 @@ impl Chip8CpuInstructions {
             // 0xBxnn Jump to Xnn+Vx
             JPX(vx_register, addr) => {
                 let x_reg_value: u16 = input.registers.peek(*vx_register) as u16;
-                let new_addr = *addr + x_reg_value;
-                input.registers.poke_i(new_addr);
+                let shifted_x_reg = x_reg_value << 8;
+                let added_addr = shifted_x_reg | addr;
+                let final_addr = added_addr + shifted_x_reg;
+                println!("JPX -> {x_reg_value:02x} {shifted_x_reg:04x} {added_addr:04x} {final_addr:04x}");
+                input.registers.poke_i(final_addr);
             }
             Chip8CpuInstructions::RND(x, byte) => {
                 // Cxkk - RND Vx, byte