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////////////////////////////////////////////////////////////////////////////

////                                                                    ////

//// T6507LP IP Core                                                    ////

////                                                                    ////

//// This file is part of the T6507LP project                           ////

//// http://www.opencores.org/cores/t6507lp/                            ////

////                                                                    ////

//// Description                                                        ////

//// 6507 FSM testbench                                                 ////

////                                                                    ////

//// Author(s):                                                         ////

//// - Gabriel Oshiro Zardo, gabrieloshiro@gmail.com                    ////

//// - Samuel Nascimento Pagliarini (creep), snpagliarini@gmail.com     ////

////                                                                    ////

////////////////////////////////////////////////////////////////////////////

////                                                                    ////

//// Copyright (C) 2001 Authors and OPENCORES.ORG                       ////

////                                                                    ////

//// This source file may be used and distributed without               ////

//// restriction provided that this copyright statement is not          ////

//// removed from the file and that any derivative work contains        ////

//// the original copyright notice and the associated disclaimer.       ////

////                                                                    ////

//// This source file is free software; you can redistribute it         ////

//// and/or modify it under the terms of the GNU Lesser General         ////

//// Public License as published by the Free Software Foundation;       ////

//// either version 2.1 of the License, or (at your option) any         ////

//// later version.                                                     ////

////                                                                    ////

//// This source is distributed in the hope that it will be             ////

//// useful, but WITHOUT ANY WARRANTY; without even the implied         ////

//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR            ////

//// PURPOSE. See the GNU Lesser General Public License for more        ////

//// details.                                                           ////

////                                                                    ////

//// You should have received a copy of the GNU Lesser General          ////

//// Public License along with this source; if not, download it         ////

//// from http://www.opencores.org/lgpl.shtml                           ////

////                                                                    ////

////////////////////////////////////////////////////////////////////////////

`include "timescale.v"

module t6507lp_fsm_tb();

        // mem_rw signals

        localparam MEM_READ = 1'b0;

        localparam MEM_WRITE = 1'b1;

        reg clk; // regs are inputs

        reg reset_n;

        reg [7:0] alu_result;

        reg [7:0] alu_status;

        reg [7:0] data_in;

        reg [7:0] alu_x;

        reg [7:0] alu_y;

        wire [12:0] address; // wires are outputs

        wire mem_rw;

        wire [7:0] data_out;

        wire [7:0] alu_opcode;

        wire [7:0] alu_a;

        wire alu_enable;

        integer my_i;

        `include "t6507lp_package.v"

        t6507lp_fsm #(8,13) t6507lp_fsm(

                .clk(clk),

                .reset_n(reset_n),

                .alu_result(alu_result),

                .alu_status(alu_status),

                .data_in(data_in),

                .alu_x(alu_x),

                .alu_y(alu_y),

                .address(address),

                .mem_rw(mem_rw),

                .data_out(data_out),

                .alu_opcode(alu_opcode),

                .alu_a(alu_a),

                .alu_enable(alu_enable)

        );

        always #10 clk = ~clk;

        reg[7:0] fake_mem[2**13-1:0];

        initial begin

                clk = 1'b0;

                reset_n = 1'b0;

                alu_result = 8'h01;

                alu_status = 8'h00;

                alu_x = 8'h07;

                alu_y = 8'h03;

                for (my_i=0; my_i < 2**13; my_i= my_i+1) begin

                        $write("\n%d",my_i);

                        fake_mem[my_i]=8'h00;

                end

                fake_mem[0] = ASL_ACC; // testing ACC mode

                fake_mem[1] = ADC_IMM; // testing IMM mode

                fake_mem[2] = 8'h27;

                fake_mem[3] = JMP_ABS; // testing ABS mode, JMP type

                fake_mem[4] = 8'h09;

                fake_mem[5] = 8'h00;

                fake_mem[6] = ASL_ACC; // wont be executed

                fake_mem[7] = ASL_ACC; // wont be executed

                fake_mem[8] = ASL_ACC; // wont be executed

                fake_mem[9] = ASL_ACC; // wont be executed

                fake_mem[10] = LDA_ABS; // testing ABS mode, READ type. A = MEM[0002]. (a=27)

                fake_mem[11] = 8'h02;

                fake_mem[12] = 8'h00;

                fake_mem[13] = ASL_ABS; // testing ABS mode, READ_MODIFY_WRITE type. should overwrite the first ASL_ACC

                fake_mem[14] = 8'h00;

                fake_mem[15] = 8'h00;

                fake_mem[16] = STA_ABS; // testing ABS mode, WRITE type. should write alu_result on MEM[1]

                fake_mem[17] = 8'h01;

                fake_mem[18] = 8'h00;

                fake_mem[19] = LDA_ZPG; // testing ZPG mode, READ type

                fake_mem[20] = 8'h00;

                fake_mem[21] = ASL_ZPG; // testing ZPG mode, READ_MODIFY_WRITE type

                fake_mem[22] = 8'h00;

                fake_mem[23] = STA_ZPG; // testing ZPG mode, WRITE type

                fake_mem[24] = 8'h00;

                fake_mem[25] = LDA_ZPX; // testing ZPX mode, READ type. A = MEM[x+1]

                fake_mem[26] = 8'h01;

                fake_mem[27] = ASL_ZPX; // testing ZPX mode, READ_MODIFY_WRITE type. MEM[x+1] = MEM[x+1] << 1;

                fake_mem[28] = 8'h01;

                fake_mem[29] = STA_ZPX; // testing ZPX mode, WRITE type. MEM[x+2] = A;

                fake_mem[30] = 8'h02;

                fake_mem[31] = LDA_ABX; // testing ABX mode, READ TYPE. No page crossed.

                fake_mem[32] = 8'h0a;

                fake_mem[33] = 8'h00;

                fake_mem[34] = LDA_ABX; // testing ABX mode, READ TYPE. Page crossed.

                fake_mem[35] = 8'hff;

                fake_mem[36] = 8'h00;

                fake_mem[37] = ASL_ABX; // testing ABX mode, READ_MODIFY_WRITE TYPE. No page crossed.

                fake_mem[38] = 8'h01;

                fake_mem[39] = 8'd35;

                fake_mem[40] = ASL_ABX; // testing ABX mode, READ_MODIFY_WRITE TYPE. Page crossed.

                fake_mem[41] = 8'hff;

                fake_mem[42] = 8'h00;

                fake_mem[40] = STA_ABX; // testing ABX mode, WRITE TYPE. No page crossed.

                fake_mem[41] = 8'h04;

                fake_mem[42] = 8'h00;

                fake_mem[43] = STA_ABX; // testing ABX mode, WRITE TYPE. Page crossed.

                fake_mem[44] = 8'hff;

                fake_mem[45] = 8'h00;

                fake_mem[46] = BNE_REL; // testing REL mode, taking a branch, no page crossed.

                fake_mem[47] = 8'h0a;

                fake_mem[58] = BNE_REL; // testing REL mode, taking a branch, page crossed.

                fake_mem[59] = 8'hff;

                fake_mem[60] = 8'hff;

                fake_mem[254] = 8'hff;

                fake_mem[256] = 8'h55; // PCL fetched from here when executing RTS_IMP

                fake_mem[257] = 8'h01;    // PCH fetched from here when executing RTS_IMP

                fake_mem[264] = 8'd340;

                fake_mem[315] = BEQ_REL; // testing REL mode, not taking a branch, page would have crossed.

                fake_mem[316] = 8'hff;

                fake_mem[317] = BEQ_REL; // testing REL mode, not taking a branch, page would not have crossed.

                fake_mem[318] = 8'h00;

                fake_mem[319] = LDA_IDX; // testing IDX mode READ TYPE, no page crossed;

                fake_mem[320] = 8'h0a;

                fake_mem[321] = LDA_IDX; // testing IDX mode READ TYPE, page crossed; this will actually do A = MEM[6] because there is no carry

                fake_mem[322] = 8'hff;

                //fake_mem[319] = SLO_IDX; // testing IDX mode READ_MODIFY_WRITE TYPE

                //fake_mem[320] = 8'h0a;   // all of read modify write instructions are not documented therefore will not be simulated

                fake_mem[323] = STA_IDX; // testing IDX mode WRITE TYPE, page crossed being ignored

                fake_mem[324] = 8'hff;

                fake_mem[325] = STA_IDX; // testing IDX mode WRITE TYPE, page not crossed;

                fake_mem[326] = 8'h00;

                fake_mem[327] = LDA_IDY; // testing IDY mode READ TYPE, page not crossed;

                fake_mem[328] = 8'h00;

                fake_mem[329] = LDA_IDY; // testing IDY mode READ TYPE, page not crossed but pointer overflowed.

                fake_mem[330] = 8'hff;

                /* testing IDY mode READ TYPE, page crossed.

                   address may assume a invalid value when page is crossed but it is fixed on the next cycle when the true read occurs.

                   this is probably not an issue */

                fake_mem[331] = LDA_IDY;

                fake_mem[332] = 8'hfe;

                fake_mem[333] = STA_IDY; // testing IDY mode WRITE TYPE, page crossed;

                fake_mem[334] = 8'h00;

                fake_mem[335] = STA_IDY; // testing IDY mode WRITE TYPE, page not crossed;

                fake_mem[336] = 8'h0e;

                fake_mem[337] = INX_IMP;

                //fake_mem[338] = JMP_IND; // testing absolute indirect addressing. page crossed when updating pointer.

                //fake_mem[339] = 8'hff; 

                //fake_mem[340] = 8'h00; 

                //fake_mem[337] = JMP_IND; // testing absolute indirect addressing. no page crossed when updating pointer.

                //fake_mem[338] = 8'h3b;   // these are commented cause they will actually jump

                //fake_mem[339] = 8'h00;

                //fake_mem[338] = BRK_IMP;

                //fake_mem[339] = RTI_IMP;

                //fake_mem[340] = RTS_IMP;

                // 341 is skipped due to RTS internal functionality

                //fake_mem[342] = PHA_IMP;      

                //fake_mem[343] = PHP_IMP;      

                //fake_mem[344] = PLA_IMP;      

                //fake_mem[345] = PLP_IMP;

                fake_mem[338] = JSR_ABS;

                fake_mem[339] = 8'h01;

                fake_mem[340] = 8'h01;

                fake_mem[8190] = 8'h53; // this is the reset vector

                fake_mem[8191] = 8'h01;

                @(negedge clk) // will wait for next negative edge of the clock (t=20)

                reset_n=1'b1;

                #4000;

                $finish; // to shut down the simulation

        end //initial

        always @(clk) begin

                if (mem_rw == MEM_READ) begin // MEM_READ

                        data_in <= fake_mem[address];

                        $write("\nreading from mem position %h: %h", address, fake_mem[address]);

                end

                else begin // MEM_WRITE

                        fake_mem[address] <= data_out;

                        $write("\nreading from mem position %h: %h", address, fake_mem[address]);

                end

        end

endmodule