Implemented BIT $n, r

First of the CB prefixed opcodes.

rtl/cpu/alu.sv

@@ -9,6 +9,7 @@ module alu (
     input logic       alu_op_valid_i,
     input alu_op_t    alu_op_i,
     input logic [7:0] operand_i,
+    input logic [2:0] inx8_i, // Only used for bit/set/res
 
     input alu16_op_t   alu16_op_i,
     input logic [15:0] inx16_i,
@@ -31,6 +32,9 @@ module alu (
     logic [ 7:0] a_xor;
     logic [ 7:0] f_xor;
 
+    logic [ 7:0] a_bit; // Never written, only to test
+    logic [ 7:0] f_bit;
+
     logic [16:0] out16_add;
     logic [ 7:0] f16_add;
     logic [15:0] out16_inc;
@@ -41,15 +45,19 @@ module alu (
 
     assign a_we   = alu_op_valid_i;
     assign a_next = (alu_op_i == ALU_OP_XOR) ? a_xor :
-                                               a_xor;
+                                               a_r;
 
     assign f_we   = alu_op_valid_i;
     assign f_next = (alu_op_i == ALU_OP_XOR) ? f_xor :
-                                               f_xor;
+                    (alu_op_i == ALU_OP_BIT) ? f_bit :
+                                               f_r;
 
     assign a_xor = (a_r ^ operand_i);
     assign f_xor = {~(|a_xor), 3'b0, f_r[3:0]};
 
+    assign a_bit = (operand_i - {4'b0, inx8_i});
+    assign f_bit = {~(|a_bit), 2'b10, f_r[4:0]};
+
     assign out16_dec = (inx16_i - 16'h01);
 
     assign a_o = a_r;