From aef21b7e7b0d391047c15dda56243e527e42411e Mon Sep 17 00:00:00 2001
From: uvok
Date: Thu, 1 Jan 2026 18:56:37 +0100
Subject: add instruction decoder

---
 nandgame/instruction_decode.sv | 58 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 nandgame/instruction_decode.sv

diff --git a/nandgame/instruction_decode.sv b/nandgame/instruction_decode.sv
new file mode 100644
index 0000000..eafd90c
--- /dev/null
+++ b/nandgame/instruction_decode.sv
@@ -0,0 +1,58 @@
+`timescale 1us/1us
+
+`include "alu.sv"
+`include "cond_check.sv"
+
+module instruction_decode  #(
+  parameter DATA_WIDTH = 16
+) (
+  input [15:0] instruction,
+  
+  input [(DATA_WIDTH-1):0] A_i,
+  input [(DATA_WIDTH-1):0] D_i,
+  input [(DATA_WIDTH-1):0] pA_i,
+  
+  output [(DATA_WIDTH-1):0] RES,
+  output do_jump,
+
+  output dst_a,
+  output dst_d,
+  output dst_pa
+);
+
+assign dst_a = instruction[5];
+assign dst_d = instruction[4];
+assign dst_pa = instruction[3];
+
+wire use_pointer_a_for_alu;
+wire [(DATA_WIDTH-1):0] alu_y;
+assign use_pointer_a_for_alu = instruction[12];
+assign alu_y = use_pointer_a_for_alu ? pA_i : A_i;
+
+wire [(DATA_WIDTH-1):0] alu_res;
+
+alu #(
+  .DATA_WIDTH(DATA_WIDTH)
+) my_alu (
+  .X(D_i),
+  .Y(alu_y),
+  .u(instruction[10]),
+  .opcode(instruction[9:8]),
+  .zx(instruction[7]),
+  .sw(instruction[6]),
+  .RES(alu_res)
+);
+
+cond_check #(
+  .DATA_WIDTH(DATA_WIDTH)
+) my_cond (
+  .X(alu_res),
+  .ltz(instruction[2]),
+  .eqz(instruction[1]),
+  .gtz(instruction[0]),
+  .res(do_jump)
+);
+
+assign RES = alu_res;
+
+endmodule
-- 
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