Initial work on reading instructions from bootROM

build/tb_top.Makefile

@@ -1,5 +1,8 @@
 TB       = tb_top
-SOURCES  = gb.sv tb_top.sv
-PATH_SRC = ../rtl:../sim/tbench
+SOURCES  = gb.sv cpu.sv registers.sv control.sv rom.sv tb_top.sv clkgen.sv
+PATH_SRC = ../rtl:../rtl/cpu:../rtl/shared:../sim/tbench:../sim/shared
+
+gb.sdb:  cpu.sdb rom.sdb
+cpu.sdb: control.sdb fetch.sdb registers.sdb
 
 include ../synthflow/vivado/Makefile.rules

rtl/cpu/control.sv

@@ -0,0 +1,49 @@
+`include "cpu_pkg.svh"
+
+import cpu_pkg::*;
+
+module control (
+    input  logic   clk_i,
+    input  logic   nreset_i,
+    output state_t state_o,
+
+    output logic [15:0] pc_o
+);
+
+    state_t state_r;
+    state_t state_next;
+
+    logic        pc_we;
+    logic [15:0] pc_r;
+    logic [15:0] pc_next;
+
+    always_ff @(posedge clk_i or negedge nreset_i) begin
+        if (~nreset_i)
+            state_r <= ST0_ADDR;
+        else
+            state_r <= state_next;
+    end
+
+    always_ff @(posedge clk_i or negedge nreset_i) begin
+        if (~nreset_i)
+            pc_r <= '0;
+        else if (pc_we)
+            pc_r <= pc_next;
+    end
+
+    assign pc_we   = (state_r == ST0_ADDR);
+    assign pc_next = (pc_r + 16'b1);
+
+    always_comb begin
+        case (state_r)
+            ST0_ADDR:     state_next = ST1_DEC;
+            ST1_DEC:      state_next = ST2_EXEC;
+            ST2_EXEC:     state_next = ST3_INC_ADDR;
+            ST3_INC_ADDR: state_next = ST0_ADDR;
+        endcase
+    end
+
+    assign state_o = state_r;
+    assign pc_o    = pc_r;
+
+endmodule : control

rtl/cpu/cpu.sv

@@ -0,0 +1,31 @@
+`include "cpu_pkg.svh"
+
+import cpu_pkg::*;
+
+module cpu (
+    input  logic clk_i,
+    input  logic nreset_i,
+
+    output logic [15:0] address_o,
+    input  logic [ 7:0] rdata_i
+);
+
+    state_t state;
+
+    logic [15:0] pc;
+
+    control control_inst (
+        .clk_i   (clk_i),
+        .nreset_i(nreset_i),
+        .state_o (state),
+        .pc_o    (pc)
+    );
+
+    registers registers_inst (
+        .clk_i   (clk_i),
+        .nreset_i(nreset_i)
+    );
+
+    assign address_o = pc;
+
+endmodule : cpu

rtl/cpu/cpu_pkg.svh

@@ -0,0 +1,10 @@
+package cpu_pkg;
+
+    typedef enum {
+        ST0_ADDR,
+        ST1_DEC,
+        ST2_EXEC,
+        ST3_INC_ADDR
+    } state_t;
+
+endpackage

rtl/cpu/registers.sv

@@ -0,0 +1,6 @@
+module registers (
+    input  logic clk_i,
+    input  logic nreset_i
+);
+
+endmodule : registers

rtl/gb.sv

@@ -3,6 +3,24 @@ module gb (
     input  logic nreset_i
 );
 
+    logic [15:0] address;
+    logic [ 7:0] rdata;
 
+    cpu cpu_inst (
+        .clk_i    (clk_i),
+        .nreset_i (nreset_i),
+        .address_o(address),
+        .rdata_i  (rdata)
+    );
+
+    rom #(
+        .FILE_NAME("DMG_ROM.bin"),
+        .ADDR_W   (8),
+        .DATA_W   (8)
+    ) rom_inst (
+        .clk_i    (clk_i),
+        .address_i(address[7:0]),
+        .rdata_o  (rdata)
+    );
 
 endmodule : gb

rtl/shared/rom.sv

@@ -0,0 +1,24 @@
+module rom #(
+    parameter string           FILE_NAME = "",
+    parameter integer unsigned ADDR_W = 8,
+    parameter integer unsigned DATA_W = 8
+) (
+    input  logic              clk_i,
+    input  logic [ADDR_W-1:0] address_i,
+
+    output logic [DATA_W-1:0] rdata_o
+);
+
+localparam ROM_SIZE = 2**ADDR_W;
+
+logic [DATA_W-1:0] rom [ROM_SIZE-1:0];
+
+always_ff @(posedge clk_i)
+    rdata_o <= rom[address_i];
+
+initial begin
+    static integer fd = $fopen(FILE_NAME, "rb");
+    void'($fread(rom, fd));
+end
+
+endmodule : rom

sim/shared/clkgen.sv

@@ -0,0 +1,18 @@
+module clkgen #(
+    PERIOD_NS      = 10,
+    RESET_DELAY_NS = 100
+) (
+    output logic clk_o,
+    output logic nreset_o
+);
+
+    initial begin
+        clk_o    <= 1'b0;
+        nreset_o <= 1'b0;
+        #RESET_DELAY_NS nreset_o <= 1'b1;
+    end
+
+    always
+        #(PERIOD_NS/2) clk_o <= ~clk_o;
+
+endmodule

sim/tbench/tb_top.sv

@@ -3,19 +3,15 @@ module tb_top ();
     logic clk;
     logic nreset;
 
+    clkgen clkgen_inst (
+        .clk_o   (clk),
+        .nreset_o(nreset)
+    );
+
     gb gb_inst (
         .clk_i   (clk),
         .nreset_i(nreset)
     );
 
-    initial begin
-        clk    = 1'b0;
-        nreset = 1'b1;
-
-        #1  nreset = 1'b0;
-        #24 nreset = 1'b1;
-    end // initial
-
-    always #5 clk = ~clk;
 
 endmodule : tb_top