diff --git a/saturn_inst_decoder.v b/saturn_inst_decoder.v
index 49fcc4b..f4725ae 100644
--- a/saturn_inst_decoder.v
+++ b/saturn_inst_decoder.v
@@ -136,6 +136,7 @@ reg [0:0] decode_started;
 
 reg [0:0] block_0x;
 reg [0:0] block_1x;
+reg [0:0] block_13x;
 reg [0:0] block_14x;
 reg [0:0] block_15x;
 reg [0:0] block_15xa;
@@ -195,6 +196,7 @@ initial begin
 
     block_0x        = 1'b0;
     block_1x        = 1'b0;
+    block_13x       = 1'b0;
     block_14x       = 1'b0;
     block_15x       = 1'b0;
     block_15xa      = 1'b0;
@@ -349,6 +351,7 @@ always @(posedge i_clk) begin
 
             if (block_1x) begin
                 case (i_nibble)
+                    4'h3: block_13x <= 1'b1;
                     4'h4: block_14x <= 1'b1;
                     4'h5: block_15x <= 1'b1;
                     4'h9, 4'hA, 4'hB, 4'hD, 4'hE, 4'hF:
@@ -371,6 +374,29 @@ always @(posedge i_clk) begin
                 block_1x        <= 1'b0;
             end
 
+            if (block_13x) begin
+                $display("DECODER  %0d: [%d] block_13x %h", i_phase, i_cycle_ctr, i_nibble);
+                o_instr_type    <=  `INSTR_TYPE_ALU;
+                if (!i_nibble[1]) begin
+                    o_alu_opcode    <= `ALU_OP_COPY;
+                    o_alu_reg_dest  <= i_nibble[0] ? `ALU_REG_D1 : `ALU_REG_D0;
+                    o_alu_reg_src_1 <= i_nibble[2] ? `ALU_REG_C  : `ALU_REG_A;
+                    o_alu_reg_src_2 <= `ALU_REG_NONE;
+                end else begin
+                    o_alu_opcode <= `ALU_OP_EXCH;
+                    o_alu_reg_dest  <= i_nibble[2] ? `ALU_REG_C  : `ALU_REG_A;
+                    o_alu_reg_src_1 <= i_nibble[0] ? `ALU_REG_D1 : `ALU_REG_D0;
+                    o_alu_reg_src_2 <= i_nibble[2] ? `ALU_REG_C  : `ALU_REG_A;
+                end
+                o_alu_ptr_begin <= 4'h0;
+                o_alu_ptr_end   <= i_nibble[3] ? 4'h3 : 4'h4;
+                o_alu_opcode    <=  i_nibble[1] ? `ALU_OP_EXCH : `ALU_OP_COPY;
+                o_instr_execute <= 1'b1;
+                o_instr_decoded <= 1'b1;
+                decode_started  <= 1'b0;
+                block_13x <= 1'b0;
+            end
+
             if (block_14x) begin
                 $display("DECODER  %0d: [%d] block_14x %h", i_phase, i_cycle_ctr, i_nibble);
                 o_mem_pointer   <= i_nibble[0];
@@ -814,6 +840,7 @@ always @(posedge i_clk) begin
 
         block_0x        <= 1'b0;
         block_1x        <= 1'b0;
+        block_13x       <= 1'b0;
         block_14x       <= 1'b0;
         block_15x       <= 1'b0;
         block_15xa      <= 1'b0;