diff --git a/src/lib.rs b/src/lib.rs
index 30bf3b6..4a0a829 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -6,6 +6,7 @@ use std::rc::Rc;
 use std::*;
 
 use memory::MemoryError;
+use stack::StackError;
 
 use crate::memory::{Memory, TrivialMemory};
 use crate::stack::Stack;
@@ -98,6 +99,15 @@ impl Device for SystemDevice {
     }
 }
 
+pub enum UxnError {
+    StackError(StackError),
+    MemoryError(MemoryError),
+    ExecutionLimit(u16),
+    ArithmeticOverflow,
+    ArithmeticUnderflow,
+    DivisionByZero,
+}
+
 #[derive(Debug)]
 pub struct Uxn {
     memory: Rc<RefCell<TrivialMemory>>,
@@ -169,4 +179,99 @@ impl Uxn {
         self.memory.borrow_mut().set2(address, val)?;
         Ok(())
     }
+
+    pub fn lda1(&mut self, address: u16) -> Result<u8, MemoryError> {
+        self.memory.borrow().get1(address)
+    }
+
+    // Run one clock cycle (instruction)
+    pub fn step(&mut self) -> Result<(), UxnError> {
+        Ok(())
+    }
+
+    pub fn run(&mut self, limit: u16) -> Result<(), UxnError> {
+        let mut executed = 0;
+        loop {
+            if executed == limit {
+                return Err(UxnError::ExecutionLimit(executed));
+            }
+            if self.is_halted() {
+                break;
+            }
+            match self.lda1(self.pc) {
+                Err(e) => return Err(UxnError::MemoryError(e)),
+                Ok(0) => break,
+                Ok(opcode) => {
+                    // Extract flags
+                    let sflag: bool = opcode & 0x20 != 0;
+                    let rflag: bool = opcode & 0x40 != 0;
+                    let kflag: bool = opcode & 0x80 != 0;
+
+                    match opcode & 0x1F {
+                        0x00 => {
+                            // LIT1
+                            ()
+                        }
+                        0x01 => {
+                            // INC1
+                            ()
+                        }
+                        0x02 => {
+                            // POP1
+                            ()
+                        }
+                        0x03 => {
+                            // NIP1
+                            ()
+                        }
+                        0x04 => {
+                            // SWP1
+                            ()
+                        }
+                        0x05 => {
+                            // ROT1
+                            ()
+                        }
+                        0x06 => {
+                            // DUP1
+                            ()
+                        }
+                        0x07 => {
+                            // OVR1
+                        }
+                        0x08 => {
+                            // EQ1
+                            ()
+                        }
+                        0x09 => {
+                            // NEQ1
+                            ()
+                        }
+                        0x0a => {
+                            // GTH1
+                            ()
+                        }
+                        0x0b => {
+                            // LTH1
+                            ()
+                        }
+                        0x0c => {
+                            // JMP1
+                        }
+                        0x0d => {
+                            // JCN1
+                        }
+                        0x0e => {
+                            // JSR1
+                        }
+
+                        _ => (),
+                    }
+                }
+            }
+
+            executed += 1;
+        }
+        Ok(())
+    }
 }