Add postindexed address mode

src/cpu.verilog

@@ -23,8 +23,10 @@ module cpu
     localparam STATE_FETCH_DATA_2 = 4;
     localparam STATE_EXECUTE_DATA_2 = 5;
     localparam STATE_BRANCH = 7;
-    localparam STATE_EXECUTE_PRE_IDX_1 = 8;
-    localparam STATE_EXECUTE_PRE_IDX_2 = 9;
+    localparam STATE_EXECUTE_IDX_1 = 8;
+    localparam STATE_EXECUTE_IDX_2 = 9;
+    localparam STATE_EXECUTE_POST_IDX_1 = 10;
+    localparam STATE_EXECUTE_POST_IDX_2 = 11;
 
 localparam
           READ_SOURCE_NONE = 2'h0,
@@ -173,6 +175,21 @@ always_comb
         begin
             {mem_aux_addr_hi, mem_aux_addr_lo} = {mem_data, mem_aux_addr} + Y;
         end
+      else if (address_code == ADDR_MODE_POSTINDEXED_INDIRECT)
+        begin
+            if (state == STATE_EXECUTE_POST_IDX_1)
+              begin
+                  {mem_aux_addr_hi, mem_aux_addr_lo} = {8'h0, mem_data};
+              end
+            else if (state == STATE_EXECUTE_POST_IDX_2)
+              begin
+                  {mem_aux_addr_hi, mem_aux_addr_lo} = {8'h0, mem_aux2_addr};
+              end
+            else
+              begin
+                  {mem_aux_addr_hi, mem_aux_addr_lo} = {mem_data, mem_aux_addr} + Y;
+              end
+        end
   end
 
 always_comb
@@ -195,13 +212,7 @@ always_comb
             alu_op_c = 1'b1;
             alu_op_sel = OP_SUB;
         end
-      else if (address_code == ADDR_MODE_IMMEDIATE ||
-               address_code == ADDR_MODE_ABSOLUTE ||
-               address_code == ADDR_MODE_INDEXED_ABSOLUTE_X ||
-               address_code == ADDR_MODE_INDEXED_ABSOLUTE_Y ||
-               address_code == ADDR_MODE_ZP ||
-               address_code == ADDR_MODE_INDEXED_ZP ||
-               address_code == ADDR_MODE_PREINDEXED_INDIRECT)
+      else
         begin
             alu_op_1 = A;
             alu_op_2 = mem_data;
@@ -330,7 +341,12 @@ always @(posedge clk)
           end
         else if (address_code == ADDR_MODE_PREINDEXED_INDIRECT)
           begin
-              state <= STATE_EXECUTE_PRE_IDX_1;
+              state <= STATE_EXECUTE_IDX_1;
+          end
+        else if(address_code == ADDR_MODE_POSTINDEXED_INDIRECT)
+          begin
+              mem_sel <= DMUX_AUX;
+              state <= STATE_EXECUTE_POST_IDX_1;
           end
         else if (address_code == ADDR_MODE_IMPLIED)
           begin
@@ -371,7 +387,22 @@ always @(posedge clk)
               mem_aux_addr <= mem_data;
           end
         mem_sel <= DMUX_PC;
-        pending_a_read <= READ_SOURCE_ALU;
+        if (decoded_instr == I_LDA)
+          begin
+              pending_a_read <= READ_SOURCE_MEM;
+          end
+        else if (decoded_instr == I_LDX)
+          begin
+              pending_x_read <= READ_SOURCE_MEM;
+          end
+        else if (decoded_instr == I_LDY)
+          begin
+              pending_y_read <= READ_SOURCE_MEM;
+          end
+        else
+          begin
+              pending_a_read <= READ_SOURCE_ALU;
+          end
 
         state <= STATE_FETCH;
     end
@@ -384,21 +415,38 @@ always @(posedge clk)
         pending_rel_branch <= 0;
         state <= STATE_FETCH;
     end
-  else if (state == STATE_EXECUTE_PRE_IDX_1)
+  else if (state == STATE_EXECUTE_IDX_1)
     begin
         mem_sel <= DMUX_AUX2;
-        mem_aux2_addr[7:0] <= mem_data + X;
+        if (address_code == ADDR_MODE_PREINDEXED_INDIRECT)
+          begin
+              mem_aux2_addr[7:0] <= mem_data + X;
+          end
+        else
+          begin
+              mem_aux2_addr[7:0] <= mem_data;
+          end
         mem_aux2_addr[15:8] <= 0;
 
-        state <= STATE_EXECUTE_PRE_IDX_2;
+        state <= STATE_EXECUTE_IDX_2;
     end
-  else if (state == STATE_EXECUTE_PRE_IDX_2)
+  else if (state == STATE_EXECUTE_IDX_2)
     begin
         mem_aux_addr <= mem_data;
         mem_aux2_addr[7:0] <= mem_aux2_addr[7:0] + 1'b1;
 
         state <= STATE_FETCH_DATA_2;
     end
+  else if (state == STATE_EXECUTE_POST_IDX_1)
+    begin
+        mem_aux2_addr <= mem_data + 1'b1;
+        state <= STATE_EXECUTE_POST_IDX_2;
+    end
+  else if (state == STATE_EXECUTE_POST_IDX_2)
+    begin
+        mem_aux_addr <= mem_data;
+        state <= STATE_EXECUTE_DATA_2;
+    end
   else if (state == STATE_FETCH_DATA_2)
     begin
         mem_aux_addr[7:0] <= mem_data;
@@ -423,6 +471,14 @@ always @(posedge clk)
               begin
                   pending_a_read <= READ_SOURCE_MEM;
               end
+            else if(decoded_instr == I_LDX)
+              begin
+                  pending_x_read <= READ_SOURCE_MEM;
+              end
+            else if(decoded_instr == I_LDY)
+              begin
+                  pending_y_read <= READ_SOURCE_MEM;
+              end
             else if(decoded_instr == I_JMP)
               begin
                   PC <= mem_addr;
@@ -463,6 +519,11 @@ always_comb
     logic f5_past_valid;
     logic f6_past_valid;
 
+    logic [7:0] f_prev_instruction;
+    logic [4:0] f_prev_addr_code;
+
+initial f_prev_instruction = 0;
+initial f_prev_addr_code = 0;
 initial f_past_valid = 0;
 initial f2_past_valid = 0;
 initial f3_past_valid = 0;
@@ -492,6 +553,18 @@ always @(posedge clk)
     if (f5_past_valid)
       f6_past_valid <= 1;
 
+    logic [7:0] f_instr_count;
+always @(posedge clk)
+    if (state == STATE_FETCH)
+      f_instr_count <= f_instr_count + 1'b1;
+
+always @(posedge clk)
+  if (f2_past_valid && state == STATE_FETCH)
+    begin
+        f_prev_instruction <= $past(decoded_instr);
+        f_prev_addr_code <= $past(address_code);
+    end
+
 always @(posedge clk)
   if (f2_past_valid && state == STATE_EXECUTE)
     if ($past(decoded_instr) == I_DEX)
@@ -582,18 +655,32 @@ always @(posedge clk)
        $past(state, 2) == STATE_EXECUTE_ZP ||
        $past(state, 2) == STATE_EXECUTE))
     begin
-        if ($past(decoded_instr, 2) == I_EOR)
+        if (f_prev_instruction == I_EOR)
           assert(A == ($past(A) ^ $past(mem_data)));
-        else if ($past(decoded_instr, 2) == I_AND)
+        else if (f_prev_instruction == I_AND)
           assert(A == ($past(A) & $past(mem_data)));
-        else if ($past(decoded_instr, 2) == I_ORA)
+        else if (f_prev_instruction == I_ORA)
           assert(A == ($past(A) | $past(mem_data)));
-        else if ($past(decoded_instr, 2) == I_ADC)
+        else if (f_prev_instruction == I_ADC)
           assert(A == ($past(A) + $past(mem_data) + $past(P[P_C])));
+        else if (f_prev_instruction == I_LDA)
+          assert(A == $past(mem_data));
+        else if (f_prev_instruction == I_LDX)
+          assert(X == $past(mem_data));
+        else if (f_prev_instruction == I_LDY)
+          assert(Y == $past(mem_data));
         else
           assume(0);
 
-        assert($past(mem_wr, 2) == 1'b0);
+        if (f_prev_instruction == I_STA)
+          begin
+              assert($past(mem_wr, 2) == 1'b1);
+              assert($past(mem_data_wr) == A);
+          end
+        else
+          begin
+              assert($past(mem_wr, 2) == 1'b0);
+          end
 
         if ($past(address_code, 2) == ADDR_MODE_ABSOLUTE)
           assert($past(f_abs_address, 2) == $past(mem_addr_eff, 2));
@@ -610,10 +697,27 @@ always @(posedge clk)
               assert($past(f_abs_address, 2) == $past(mem_addr_eff, 2));
               assert($past(mem_addr_eff, 4) == (($past(mem_data, 5) + $past(X, 5)) & 8'hff));
           end
+        else if ($past(address_code, 2) == ADDR_MODE_POSTINDEXED_INDIRECT)
+          begin
+              assert(($past(f_abs_address, 2) + $past(Y, 2)) == $past(mem_addr_eff, 2));
+          end
 
-        assert(P[P_Z] == (A == 0));
-        assert(P[P_N] == (A[7] == 1));
-        if ($past(decoded_instr) == I_ADC)
+        if (f_prev_instruction == I_LDX)
+            begin
+                assert(P[P_Z] == (X == 0));
+                assert(P[P_N] == (X[7] == 1));
+            end
+        else if (f_prev_instruction == I_LDY)
+            begin
+                assert(P[P_Z] == (Y == 0));
+                assert(P[P_N] == (Y[7] == 1));
+            end
+        else
+          begin
+              assert(P[P_Z] == (A == 0));
+              assert(P[P_N] == (A[7] == 1));
+          end
+        if (f_prev_instruction == I_ADC)
           begin
               assert(P[P_C] == ({1'b0, $past(A)} +
                                 {1'b0, $past(mem_data)} +
@@ -629,8 +733,14 @@ always @(posedge clk)
         assert(P[P_D] == $past(P[P_D], 2));
         assert(P[P_I] == $past(P[P_I], 2));
         assert(S == $past(S, 2));
-        assert(X == $past(X, 2));
-        assert(Y == $past(Y, 2));
+        if (f_prev_instruction != I_LDX)
+          begin
+              assert(X == $past(X, 2));
+          end
+        if (f_prev_instruction != I_LDY)
+          begin
+              assert(Y == $past(Y, 2));
+          end
 
         if (f3_past_valid)
           begin
@@ -680,28 +790,106 @@ always @(posedge clk)
 always @(posedge clk)
   cover(state == STATE_EXECUTE);
 
+always @(posedge clk)
+  cover(f_instr_count > 16);
+
+always @(posedge clk)
+  begin
+      if (decoded_instr == I_ADC)
+        begin
+            cover(address_code == ADDR_MODE_IMMEDIATE);
+            cover(address_code == ADDR_MODE_ABSOLUTE);
+            cover(address_code == ADDR_MODE_ZP);
+            cover(address_code == ADDR_MODE_INDEXED_ABSOLUTE_X);
+            cover(address_code == ADDR_MODE_INDEXED_ABSOLUTE_Y);
+            cover(address_code == ADDR_MODE_INDEXED_ZP);
+            cover(address_code == ADDR_MODE_PREINDEXED_INDIRECT);
+        end
+  end
+
+always @(posedge clk)
+  begin
+      if (decoded_instr == I_LDA)
+        begin
+            cover(address_code == ADDR_MODE_IMMEDIATE);
+            cover(address_code == ADDR_MODE_ABSOLUTE);
+            cover(address_code == ADDR_MODE_ZP);
+            cover(address_code == ADDR_MODE_INDEXED_ABSOLUTE_X);
+            cover(address_code == ADDR_MODE_INDEXED_ABSOLUTE_Y);
+            cover(address_code == ADDR_MODE_INDEXED_ZP);
+            cover(address_code == ADDR_MODE_PREINDEXED_INDIRECT);
+        end
+  end
+
+always @(posedge clk)
+  begin
+      if (decoded_instr == I_LDX)
+        begin
+            cover(address_code == ADDR_MODE_IMMEDIATE);
+            cover(address_code == ADDR_MODE_ABSOLUTE);
+            cover(address_code == ADDR_MODE_ZP);
+            cover(address_code == ADDR_MODE_INDEXED_ABSOLUTE_Y);
+            cover(address_code == ADDR_MODE_INDEXED_ZP);
+        end
+  end
+
+always @(posedge clk)
+  begin
+      if (decoded_instr == I_EOR)
+        begin
+            cover(address_code == ADDR_MODE_IMMEDIATE);
+            cover(address_code == ADDR_MODE_ABSOLUTE);
+            cover(address_code == ADDR_MODE_ZP);
+            cover(address_code == ADDR_MODE_INDEXED_ABSOLUTE_X);
+            cover(address_code == ADDR_MODE_INDEXED_ABSOLUTE_Y);
+            cover(address_code == ADDR_MODE_INDEXED_ZP);
+            cover(address_code == ADDR_MODE_PREINDEXED_INDIRECT);
+        end
+  end
+
+always @(posedge clk)
+  begin
+      if (decoded_instr == I_AND)
+        begin
+            cover(address_code == ADDR_MODE_IMMEDIATE);
+            cover(address_code == ADDR_MODE_ABSOLUTE);
+            cover(address_code == ADDR_MODE_ZP);
+            cover(address_code == ADDR_MODE_INDEXED_ABSOLUTE_X);
+            cover(address_code == ADDR_MODE_INDEXED_ABSOLUTE_Y);
+            cover(address_code == ADDR_MODE_INDEXED_ZP);
+            cover(address_code == ADDR_MODE_PREINDEXED_INDIRECT);
+        end
+  end
+
 always @(posedge clk)
   begin
-      cover(decoded_instr == I_ADC && address_code == ADDR_MODE_IMMEDIATE);
-      cover(decoded_instr == I_ADC && address_code == ADDR_MODE_ABSOLUTE);
-      cover(decoded_instr == I_ADC && address_code == ADDR_MODE_ZP);
-      cover(decoded_instr == I_ADC && address_code == ADDR_MODE_INDEXED_ABSOLUTE_X);
-      cover(decoded_instr == I_ADC && address_code == ADDR_MODE_INDEXED_ABSOLUTE_Y);
-      cover(decoded_instr == I_ADC && address_code == ADDR_MODE_INDEXED_ZP);
-      cover(decoded_instr == I_ADC && address_code == ADDR_MODE_PREINDEXED_INDIRECT);
+      if (decoded_instr == I_ORA)
+        begin
+            cover(address_code == ADDR_MODE_IMMEDIATE);
+            cover(address_code == ADDR_MODE_ABSOLUTE);
+            cover(address_code == ADDR_MODE_ZP);
+            cover(address_code == ADDR_MODE_INDEXED_ABSOLUTE_X);
+            cover(address_code == ADDR_MODE_INDEXED_ABSOLUTE_Y);
+            cover(address_code == ADDR_MODE_INDEXED_ZP);
+            cover(address_code == ADDR_MODE_PREINDEXED_INDIRECT);
+        end
   end
 
 always @(posedge clk)
   begin
-      cover(decoded_instr == I_LDA && address_code == ADDR_MODE_IMMEDIATE);
-      cover(decoded_instr == I_LDA && address_code == ADDR_MODE_ABSOLUTE);
-      cover(decoded_instr == I_LDA && address_code == ADDR_MODE_ZP);
-      cover(decoded_instr == I_LDA && address_code == ADDR_MODE_INDEXED_ABSOLUTE_X);
-      cover(decoded_instr == I_LDA && address_code == ADDR_MODE_INDEXED_ABSOLUTE_Y);
-      cover(decoded_instr == I_LDA && address_code == ADDR_MODE_INDEXED_ZP);
-      cover(decoded_instr == I_LDA && address_code == ADDR_MODE_PREINDEXED_INDIRECT);
+      if (decoded_instr == I_DEX)
+        begin
+            cover(address_code == ADDR_MODE_IMPLIED);
+        end
   end
 
+always @(posedge clk)
+  begin
+      if (decoded_instr == I_DEY)
+        begin
+            cover(address_code == ADDR_MODE_IMPLIED);
+        end
+  end
 `endif
 
 endmodule