From 8c0b7ea39d57cb6c80cf66207291837d95c71940 Mon Sep 17 00:00:00 2001
From: Julian Blake Kongslie
Date: Mon, 5 Apr 2021 13:32:41 -0700
Subject: Change the null byte from no-op to halt.

---
 asm.rb      | 2 +-
 hdl/top.sv  | 2 +-
 mem/mem.hex | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/asm.rb b/asm.rb
index 686f9c1..c94ecf7 100755
--- a/asm.rb
+++ b/asm.rb
@@ -12,7 +12,7 @@ OPCODES = {
   "++acc" => 0x002,
   "--acc" => 0x004,
   "tx"    => 0x040,
-  "halt"  => 0x080,
+  "halt"  => 0x000,
   }
 
 Line = Struct.new(:opcode, :refs, :code)
diff --git a/hdl/top.sv b/hdl/top.sv
index 54cfdc5..a1cdbf7 100644
--- a/hdl/top.sv
+++ b/hdl/top.sv
@@ -133,7 +133,7 @@ always_ff @(posedge clk) begin
                             if (operand[1]) ++acc;
                             if (operand[2]) --acc;
                             if (operand[6]) state = MEMORY;
-                            if (operand[7]) state = HALT;
+                            if (operand == 0) state = HALT;
                         end
                         'h1: acc = sign_extended_operand;
                         'h2, 'h3: begin
diff --git a/mem/mem.hex b/mem/mem.hex
index a0c98e5..84caf6d 100644
--- a/mem/mem.hex
+++ b/mem/mem.hex
@@ -84,7 +84,7 @@
 548 // jmp fibloop
 121 // fullydone: acc= 0x21
 040 // tx
-080 // halt
+000 // halt
 
 @70
 
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