diff --git a/src/opcodes.c b/src/opcodes.c
index 4416d4f..490cb4e 100644
--- a/src/opcodes.c
+++ b/src/opcodes.c
@@ -39,6 +39,9 @@ Instruction instructions[OPCODECOUNT] = {
     CMP  - 1000 0XXX CMP REG, REG
          - 1000 1XXX CMP REG, Constant
          - 1001 0XXX CMP REG, Address
+    //Read from port specified by either a register or a constant
+    IN   - 1100 0XXX IN REG
+         - 1101 0XXX IN Constant
 
     OUT  - 1111 1XXX OUT REG
 */
@@ -46,6 +49,7 @@ Instruction instructions[OPCODECOUNT] = {
 //ADD       010X XXXX
 //SUB       011X XXXX
 //CMP       100X XXXX
+//IN        110X XXXX
 //REG       XXX0 0XXX
 //Constant  XXX0 1XXX
 //Address   XXX1 0XXX