From 9f4ac4dc09c9ccb93c6b1d9726bc7543ff09de00 Mon Sep 17 00:00:00 2001
From: Rutherther <rutherther@proton.me>
Date: Sun, 29 Oct 2023 19:35:11 +0100
Subject: [PATCH] fix: jump according to zero flag, not LSB zero!!

---
 src/cpu.sv                 | 2 +-
 src/instruction_decoder.sv | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/cpu.sv b/src/cpu.sv
index 1f4542d71e7fd8825dd1c4d2b00f119e3c649c97..c734df3825ab05bba8cb3c94a243e0fea484f62c 100755
--- a/src/cpu.sv
+++ b/src/cpu.sv
@@ -75,7 +75,7 @@ module cpu(
   end
 
   // pc source
-  assign jump_taken = jump_instruction && (alu_out[0] ^ jump_negate_zero);
+  assign jump_taken = jump_instruction && (alu_zero ^ jump_negate_zero);
   always_comb begin
     case (pc_src)
       PC_PLUS : begin
diff --git a/src/instruction_decoder.sv b/src/instruction_decoder.sv
index da48bfe90c360fb54543855281b57e88b34cf0a2..a33dd7926c351da27d248b913e0d38a9212a94a3 100755
--- a/src/instruction_decoder.sv
+++ b/src/instruction_decoder.sv
@@ -152,18 +152,18 @@ module instruction_decoder(
       end
       3'b100 : begin // blt
         alu_jump_op = 3'b010;
+        jump_negate_zero = 1'b1;
         // less than 011
       end
       3'b101 : begin // bge
         alu_jump_op = 3'b010;
-        jump_negate_zero = 1'b1;
       end
       3'b110 : begin // bltu
         alu_jump_op = 3'b011;
+        jump_negate_zero = 1'b1;
       end
       3'b111 : begin // bgeu
         alu_jump_op = 3'b011;
-        jump_negate_zero = 1'b1;
       end
       default : ;
     endcase