module uc(
        clk,
        rst,
        ri,
        ind,
        regs_addr,
        regs_oe,
        regs_we,
        alu_oe,
        alu_carry,
        alu_opcode,
        ram_oe,
        ram_we,
        io_oe,
        io_we,
        cp_oe,
        cp_we,
        ind_sel,
        ind_oe,
        ind_we,
        am_oe,
        am_we,
        aie_oe,
        aie_we,
        t1_oe,
        t1_we,
        t2_oe,
        t2_we,
        ri_oe,
        ri_we,
        disp_state
    );

parameter word_width =          16;
parameter state_width =         16;

input                           clk;
input                           rst;
input [word_width-1 : 0]        ri;
input [word_width-1 : 0]        ind;
output reg                      alu_oe;
output reg                      alu_carry;
output reg[3 : 0]               alu_opcode;
output reg                      ram_oe;
output reg                      ram_we;
output reg                      io_oe;
output reg                      io_we;
output reg[2 : 0]               regs_addr;
output reg                      regs_oe;
output reg                      regs_we;
output reg                      cp_oe;
output reg                      cp_we;
output reg                      ind_sel;        // controls IND register input (0 = bus, 1 = alu flags)
output reg                      ind_oe;
output reg                      ind_we;
output reg                      am_oe;
output reg                      am_we;
output reg                      aie_oe;
output reg                      aie_we;
output reg                      t1_oe;
output reg                      t1_we;
output reg                      t2_oe;
output reg                      t2_we;
output reg                      ri_oe;          // controls RI register output which generates the offset for Jcond instructions
output reg                      ri_we;
output[state_width-1 : 0]       disp_state;

`define reset                   'h00            // reset state
`define fetch                   'h10            // load instruction to instruction register

reg [state_width-1 : 0] state = `reset, state_next;

// FSM - sequential part
always @(posedge clk) begin
    state <= `reset;

    if(!rst)
        state <= state_next;
end

// FSM - combinational part
always @(*) begin
    state_next = `reset;
    alu_oe = 0;
    alu_carry = 0;
    alu_opcode = 0;
    ram_oe = 0;
    ram_we = 0;
    io_oe = 0;
    io_we = 0;
    regs_addr = 0;
    regs_oe = 0;
    regs_we = 0;
    cp_oe = 0;
    cp_we = 0;
    ind_sel = 0;
    ind_oe = 0;
    ind_we = 0;
    am_oe = 0;
    am_we = 0;
    aie_oe = 0;
    aie_we = 0;
    t1_oe = 0;
    t1_we = 0;
    t2_oe = 0;
    t2_we = 0;
    ri_oe = 0;
    ri_we = 0;

    case(state)
        `reset: begin
            state_next = `fetch;
        end

        `fetch: begin
            cp_oe = 1;
            am_we = 1;

            state_next = `fetch + 1;
        end

        `fetch + 'd1: begin
            am_oe = 1;

            state_next = `fetch + 2;
        end

        `fetch + 'd2: begin
            ram_oe = 1;
            ri_we = 1;

            state_next = `reset;
        end

        default: ;
    endcase
end

assign disp_state = state;

endmodule