add step by

src/main.rs

@@ -21,6 +21,10 @@ struct Args {
     /// Just run BootROM
     #[arg(long)]
     run_bootrom: bool,
+
+    /// Step emulation by...
+    #[arg(long)]
+    step_by: Option<usize>,
 }
 
 type Address = u16;
@@ -177,11 +181,16 @@ fn main() {
         memory: Memory::init(run_rom),
         state,
     };
-    loop {
-        for _ in 0..10 {
-            cpu.exec_next();
-        }
-        pause();
+    match args.step_by {
+        Some(step_size) => loop {
+            for _ in 0..step_size {
+                cpu.exec_next();
+            }
+            pause();
+        },
+        None => loop {
+            cpu.exec_next()
+        },
     }
 }