diff --git a/decode1.vhdl b/decode1.vhdl
index e9dae1e..8a6804d 100644
--- a/decode1.vhdl
+++ b/decode1.vhdl
@@ -337,7 +337,7 @@ architecture behaviour of decode1 is
 
         --                                       unit     internal      in1         in2          in3   out   CR   CR   inv  inv  cry   cry  ldst  BR   sgn  upd  rsrv 32b  sgn  rc    lk   sgl
         --                                                      op                                           in   out   A   out  in    out  len        ext                                 pipe
-        constant attn_instr    : decode_rom_t := (ALU,    OP_ILLEGAL,   NONE,       NONE,        NONE, NONE, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '1');
+        constant attn_instr    : decode_rom_t := (ALU,    OP_ATTN,      NONE,       NONE,        NONE, NONE, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '1');
 	constant nop_instr     : decode_rom_t := (ALU,    OP_NOP,       NONE,       NONE,        NONE, NONE, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '0');
         constant sim_cfg_instr : decode_rom_t := (ALU,    OP_SIM_CONFIG,NONE,       NONE,        NONE, RT,   '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '1');
 
diff --git a/execute1.vhdl b/execute1.vhdl
index 4703049..0d92266 100644
--- a/execute1.vhdl
+++ b/execute1.vhdl
@@ -369,6 +369,9 @@ begin
 	    when OP_ILLEGAL =>
 		terminate_out <= '1';
 		report "illegal";
+	    when OP_ATTN =>
+		terminate_out <= '1';
+		report "ATTN";
 	    when OP_NOP =>
 		-- Do nothing
 	    when OP_ADD | OP_CMP =>