LDH A,(C) and LDH (C), A

[fpgaboy.git] / GBZ80Core.v

diff --git a/GBZ80Core.v b/GBZ80Core.v
index cb80cb8fcfe008cd0a85c16dc8e9a796fc1acc13..1d06b12f1bfd3cd10d752cd166e0d8a195c1d9d8 100644 (file)
--- a/GBZ80Core.v
+++ b/GBZ80Core.v
@@ -29,7 +29,8 @@
 `define INSN_LD_reg_imm16      8'b00xx0001
 `define INSN_LD_SP_HL          8'b11111001
 `define INSN_PUSH_reg          8'b11xx0101
-`define INSN_POP_reg           8'b11xx0001
+`define INSN_POP_reg                   8'b11xx0001
+`define INSN_LDH_AC                    8'b111x0010     // Either LDH A,(C) or LDH (C),A
 `define INSN_reg_A             3'b111
 `define INSN_reg_B             3'b000
 `define INSN_reg_C             3'b001
@@ -70,18 +71,18 @@ module GBZ80Core(
        assign busdata = buswr ? buswdata : 8'bzzzzzzzz;
        
        initial begin
-               registers[ 0] = 0;
-               registers[ 1] = 0;
-               registers[ 2] = 0;
-               registers[ 3] = 0;
-               registers[ 4] = 0;
-               registers[ 5] = 0;
-               registers[ 6] = 0;
-               registers[ 7] = 0;
-               registers[ 8] = 0;
-               registers[ 9] = 0;
-               registers[10] = 0;
-               registers[11] = 0;
+               registers[ 0] <= 0;
+               registers[ 1] <= 0;
+               registers[ 2] <= 0;
+               registers[ 3] <= 0;
+               registers[ 4] <= 0;
+               registers[ 5] <= 0;
+               registers[ 6] <= 0;
+               registers[ 7] <= 0;
+               registers[ 8] <= 0;
+               registers[ 9] <= 0;
+               registers[10] <= 0;
+               registers[11] <= 0;
        end
 
        always @(posedge clk)
@@ -266,6 +267,23 @@ module GBZ80Core(
                                        end
                                endcase
                        end
+                       `INSN_LDH_AC: begin
+                               case (cycle)
+                               0:      begin
+                                               address <= {8'hFF,registers[`REG_C]};
+                                               if (opcode[4]) begin    // LD A,(C)
+                                                       rd <= 1;
+                                               end else begin
+                                                       wr <= 1;
+                                                       wdata <= {8'hFF,registers[`REG_A]};
+                                               end
+                                       end
+                               1: begin
+                                               `EXEC_NEWCYCLE;
+                                               `EXEC_INC_PC;
+                                       end
+                               endcase
+                       end
                        default:
                                $stop;
                        endcase
@@ -364,12 +382,12 @@ module GBZ80Core(
                        `INSN_PUSH_reg: begin   /* PUSH is 16 cycles! */
                                case (cycle)
                                0: begin
-                                               {registers[`REG_SPH],registers[`REG_SPL]} =
+                                               {registers[`REG_SPH],registers[`REG_SPL]} <=
                                                        {registers[`REG_SPH],registers[`REG_SPL]} - 1;
                                                cycle <= 1;
                                        end
                                1:      begin
-                                               {registers[`REG_SPH],registers[`REG_SPL]} =
+                                               {registers[`REG_SPH],registers[`REG_SPL]} <=
                                                        {registers[`REG_SPH],registers[`REG_SPL]} - 1;
                                                cycle <= 2;
                                        end
@@ -381,7 +399,7 @@ module GBZ80Core(
                                case (cycle)
                                0:      begin
                                                cycle <= 1;
-                                               {registers[`REG_SPH],registers[`REG_SPL]} =
+                                               {registers[`REG_SPH],registers[`REG_SPL]} <=
                                                        {registers[`REG_SPH],registers[`REG_SPL]} + 1;
                                        end
                                1:      begin
@@ -391,7 +409,7 @@ module GBZ80Core(
                                                `INSN_stack_DE: registers[`REG_E] <= rdata;
                                                `INSN_stack_HL: registers[`REG_L] <= rdata;
                                                endcase
-                                               {registers[`REG_SPH],registers[`REG_SPL]} =
+                                               {registers[`REG_SPH],registers[`REG_SPL]} <=
                                                        {registers[`REG_SPH],registers[`REG_SPL]} + 1;
                                                cycle <= 2;
                                        end
@@ -405,7 +423,17 @@ module GBZ80Core(
                                                cycle <= 0;
                                        end
                                endcase
-                       end     
+                       end
+                       `INSN_LDH_AC: begin
+                               case (cycle)
+                               0:      cycle <= 1;
+                               1: begin
+                                               cycle <= 0;
+                                               if (opcode[4])
+                                                       registers[`REG_A] <= rdata;
+                                       end
+                               endcase
+                       end
                        endcase
                        state <= `STATE_FETCH;
                end