module axi_adapter_wr #
(
    // Width of address bus in bits
    parameter ADDR_WIDTH = 32,
    // Width of input (slave) interface data bus in bits
    parameter S_DATA_WIDTH = 32,
    // Width of input (slave) interface wstrb (width of data bus in words)
    parameter S_STRB_WIDTH = (S_DATA_WIDTH/8),
    // Width of output (master) interface data bus in bits
    parameter M_DATA_WIDTH = 32,
    // Width of output (master) interface wstrb (width of data bus in words)
    parameter M_STRB_WIDTH = (M_DATA_WIDTH/8),
    // Width of ID signal
    parameter ID_WIDTH = 8,
    // Propagate awuser signal
    parameter AWUSER_ENABLE = 0,
    // Width of awuser signal
    parameter AWUSER_WIDTH = 1,
    // Propagate wuser signal
    parameter WUSER_ENABLE = 0,
    // Width of wuser signal
    parameter WUSER_WIDTH = 1,
    // Propagate buser signal
    parameter BUSER_ENABLE = 0,
    // Width of buser signal
    parameter BUSER_WIDTH = 1,
    // When adapting to a wider bus, re-pack full-width burst instead of passing through narrow burst if possible
    parameter CONVERT_BURST = 1,
    // When adapting to a wider bus, re-pack all bursts instead of passing through narrow burst if possible
    parameter CONVERT_NARROW_BURST = 0,
    // Forward ID through adapter
    parameter FORWARD_ID = 0
)
(
    input  wire                     clk,
    input  wire                     rst,

    /*
     * AXI slave interface
     */
    input  wire [ID_WIDTH-1:0]      s_axi_awid,
    input  wire [ADDR_WIDTH-1:0]    s_axi_awaddr,
    input  wire [7:0]               s_axi_awlen,
    input  wire [2:0]               s_axi_awsize,
    input  wire [1:0]               s_axi_awburst,
    input  wire                     s_axi_awlock,
    input  wire [3:0]               s_axi_awcache,
    input  wire [2:0]               s_axi_awprot,
    input  wire [3:0]               s_axi_awqos,
    input  wire [3:0]               s_axi_awregion,
    input  wire [AWUSER_WIDTH-1:0]  s_axi_awuser,
    input  wire                     s_axi_awvalid,
    output wire                     s_axi_awready,
    input  wire [S_DATA_WIDTH-1:0]  s_axi_wdata,
    input  wire [S_STRB_WIDTH-1:0]  s_axi_wstrb,
    input  wire                     s_axi_wlast,
    input  wire [WUSER_WIDTH-1:0]   s_axi_wuser,
    input  wire                     s_axi_wvalid,
    output wire                     s_axi_wready,
    output wire [ID_WIDTH-1:0]      s_axi_bid,
    output wire [1:0]               s_axi_bresp,
    output wire [BUSER_WIDTH-1:0]   s_axi_buser,
    output wire                     s_axi_bvalid,
    input  wire                     s_axi_bready,

    /*
     * AXI master interface
     */
    output wire [ID_WIDTH-1:0]      m_axi_awid,
    output wire [ADDR_WIDTH-1:0]    m_axi_awaddr,
    output wire [7:0]               m_axi_awlen,
    output wire [2:0]               m_axi_awsize,
    output wire [1:0]               m_axi_awburst,
    output wire                     m_axi_awlock,
    output wire [3:0]               m_axi_awcache,
    output wire [2:0]               m_axi_awprot,
    output wire [3:0]               m_axi_awqos,
    output wire [3:0]               m_axi_awregion,
    output wire [AWUSER_WIDTH-1:0]  m_axi_awuser,
    output wire                     m_axi_awvalid,
    input  wire                     m_axi_awready,
    output wire [M_DATA_WIDTH-1:0]  m_axi_wdata,
    output wire [M_STRB_WIDTH-1:0]  m_axi_wstrb,
    output wire                     m_axi_wlast,
    output wire [WUSER_WIDTH-1:0]   m_axi_wuser,
    output wire                     m_axi_wvalid,
    input  wire                     m_axi_wready,
    input  wire [ID_WIDTH-1:0]      m_axi_bid,
    input  wire [1:0]               m_axi_bresp,
    input  wire [BUSER_WIDTH-1:0]   m_axi_buser,
    input  wire                     m_axi_bvalid,
    output wire                     m_axi_bready
);

parameter S_ADDR_BIT_OFFSET = $clog2(S_STRB_WIDTH);
parameter M_ADDR_BIT_OFFSET = $clog2(M_STRB_WIDTH);
parameter S_WORD_WIDTH = S_STRB_WIDTH;
parameter M_WORD_WIDTH = M_STRB_WIDTH;
parameter S_WORD_SIZE = S_DATA_WIDTH/S_WORD_WIDTH;
parameter M_WORD_SIZE = M_DATA_WIDTH/M_WORD_WIDTH;
parameter S_BURST_SIZE = $clog2(S_STRB_WIDTH);
parameter M_BURST_SIZE = $clog2(M_STRB_WIDTH);

// output bus is wider
parameter EXPAND = M_STRB_WIDTH > S_STRB_WIDTH;
parameter DATA_WIDTH = EXPAND ? M_DATA_WIDTH : S_DATA_WIDTH;
parameter STRB_WIDTH = EXPAND ? M_STRB_WIDTH : S_STRB_WIDTH;
// required number of segments in wider bus
parameter SEGMENT_COUNT = EXPAND ? (M_STRB_WIDTH / S_STRB_WIDTH) : (S_STRB_WIDTH / M_STRB_WIDTH);
// data width and keep width per segment
parameter SEGMENT_DATA_WIDTH = DATA_WIDTH / SEGMENT_COUNT;
parameter SEGMENT_STRB_WIDTH = STRB_WIDTH / SEGMENT_COUNT;

// bus width assertions
initial begin
    if (S_WORD_SIZE * S_STRB_WIDTH != S_DATA_WIDTH) begin
        $error("Error: AXI slave interface data width not evenly divisble (instance %m)");
        $finish;
    end

    if (M_WORD_SIZE * M_STRB_WIDTH != M_DATA_WIDTH) begin
        $error("Error: AXI master interface data width not evenly divisble (instance %m)");
        $finish;
    end

    if (S_WORD_SIZE != M_WORD_SIZE) begin
        $error("Error: word size mismatch (instance %m)");
        $finish;
    end

    if (2**$clog2(S_WORD_WIDTH) != S_WORD_WIDTH) begin
        $error("Error: AXI slave interface word width must be even power of two (instance %m)");
        $finish;
    end

    if (2**$clog2(M_WORD_WIDTH) != M_WORD_WIDTH) begin
        $error("Error: AXI master interface word width must be even power of two (instance %m)");
        $finish;
    end
end

localparam [1:0]
    STATE_IDLE = 2'd0,
    STATE_DATA = 2'd1,
    STATE_DATA_2 = 2'd2,
    STATE_RESP = 2'd3;

reg [1:0] state_reg = STATE_IDLE, state_next;

reg [ID_WIDTH-1:0] id_reg = {ID_WIDTH{1'b0}}, id_next;
reg [ADDR_WIDTH-1:0] addr_reg = {ADDR_WIDTH{1'b0}}, addr_next;
reg [DATA_WIDTH-1:0] data_reg = {DATA_WIDTH{1'b0}}, data_next;
reg [STRB_WIDTH-1:0] strb_reg = {STRB_WIDTH{1'b0}}, strb_next;
reg [WUSER_WIDTH-1:0] wuser_reg = {WUSER_WIDTH{1'b0}}, wuser_next;
reg [7:0] burst_reg = 8'd0, burst_next;
reg [2:0] burst_size_reg = 3'd0, burst_size_next;
reg [7:0] master_burst_reg = 8'd0, master_burst_next;
reg [2:0] master_burst_size_reg = 3'd0, master_burst_size_next;
reg burst_active_reg = 1'b0, burst_active_next;
reg first_transfer_reg = 1'b0, first_transfer_next;

reg s_axi_awready_reg = 1'b0, s_axi_awready_next;
reg s_axi_wready_reg = 1'b0, s_axi_wready_next;
reg [ID_WIDTH-1:0] s_axi_bid_reg = {ID_WIDTH{1'b0}}, s_axi_bid_next;
reg [1:0] s_axi_bresp_reg = 2'd0, s_axi_bresp_next;
reg [BUSER_WIDTH-1:0] s_axi_buser_reg = {BUSER_WIDTH{1'b0}}, s_axi_buser_next;
reg s_axi_bvalid_reg = 1'b0, s_axi_bvalid_next;

reg [ID_WIDTH-1:0] m_axi_awid_reg = {ID_WIDTH{1'b0}}, m_axi_awid_next;
reg [ADDR_WIDTH-1:0] m_axi_awaddr_reg = {ADDR_WIDTH{1'b0}}, m_axi_awaddr_next;
reg [7:0] m_axi_awlen_reg = 8'd0, m_axi_awlen_next;
reg [2:0] m_axi_awsize_reg = 3'd0, m_axi_awsize_next;
reg [1:0] m_axi_awburst_reg = 2'd0, m_axi_awburst_next;
reg m_axi_awlock_reg = 1'b0, m_axi_awlock_next;
reg [3:0] m_axi_awcache_reg = 4'd0, m_axi_awcache_next;
reg [2:0] m_axi_awprot_reg = 3'd0, m_axi_awprot_next;
reg [3:0] m_axi_awqos_reg = 4'd0, m_axi_awqos_next;
reg [3:0] m_axi_awregion_reg = 4'd0, m_axi_awregion_next;
reg [AWUSER_WIDTH-1:0] m_axi_awuser_reg = {AWUSER_WIDTH{1'b0}}, m_axi_awuser_next;
reg m_axi_awvalid_reg = 1'b0, m_axi_awvalid_next;
reg m_axi_bready_reg = 1'b0, m_axi_bready_next;

// internal datapath
reg  [M_DATA_WIDTH-1:0] m_axi_wdata_int;
reg  [M_STRB_WIDTH-1:0] m_axi_wstrb_int;
reg                     m_axi_wlast_int;
reg  [WUSER_WIDTH-1:0]  m_axi_wuser_int;
reg                     m_axi_wvalid_int;
reg                     m_axi_wready_int_reg = 1'b0;
wire                    m_axi_wready_int_early;

assign s_axi_awready = s_axi_awready_reg;
assign s_axi_wready = s_axi_wready_reg;
assign s_axi_bid = s_axi_bid_reg;
assign s_axi_bresp = s_axi_bresp_reg;
assign s_axi_buser = BUSER_ENABLE ? s_axi_buser_reg : {BUSER_WIDTH{1'b0}};
assign s_axi_bvalid = s_axi_bvalid_reg;

assign m_axi_awid = FORWARD_ID ? m_axi_awid_reg : {ID_WIDTH{1'b0}};
assign m_axi_awaddr = m_axi_awaddr_reg;
assign m_axi_awlen = m_axi_awlen_reg;
assign m_axi_awsize = m_axi_awsize_reg;
assign m_axi_awburst = m_axi_awburst_reg;
assign m_axi_awlock = m_axi_awlock_reg;
assign m_axi_awcache = m_axi_awcache_reg;
assign m_axi_awprot = m_axi_awprot_reg;
assign m_axi_awqos = m_axi_awqos_reg;
assign m_axi_awregion = m_axi_awregion_reg;
assign m_axi_awuser = AWUSER_ENABLE ? m_axi_awuser_reg : {AWUSER_WIDTH{1'b0}};
assign m_axi_awvalid = m_axi_awvalid_reg;
assign m_axi_bready = m_axi_bready_reg;

integer i;

always @* begin
    state_next = STATE_IDLE;

    id_next = id_reg;
    addr_next = addr_reg;
    data_next = data_reg;
    strb_next = strb_reg;
    wuser_next = wuser_reg;
    burst_next = burst_reg;
    burst_size_next = burst_size_reg;
    master_burst_next = master_burst_reg;
    master_burst_size_next = master_burst_size_reg;
    burst_active_next = burst_active_reg;
    first_transfer_next = first_transfer_reg;

    s_axi_awready_next = 1'b0;
    s_axi_wready_next = 1'b0;
    s_axi_bid_next = s_axi_bid_reg;
    s_axi_bresp_next = s_axi_bresp_reg;
    s_axi_buser_next = s_axi_buser_reg;
    s_axi_bvalid_next = s_axi_bvalid_reg && !s_axi_bready;
    m_axi_awid_next = m_axi_awid_reg;
    m_axi_awaddr_next = m_axi_awaddr_reg;
    m_axi_awlen_next = m_axi_awlen_reg;
    m_axi_awsize_next = m_axi_awsize_reg;
    m_axi_awburst_next = m_axi_awburst_reg;
    m_axi_awlock_next = m_axi_awlock_reg;
    m_axi_awcache_next = m_axi_awcache_reg;
    m_axi_awprot_next = m_axi_awprot_reg;
    m_axi_awqos_next = m_axi_awqos_reg;
    m_axi_awregion_next = m_axi_awregion_reg;
    m_axi_awuser_next = m_axi_awuser_reg;
    m_axi_awvalid_next = m_axi_awvalid_reg && !m_axi_awready;
    m_axi_bready_next = 1'b0;

    if (SEGMENT_COUNT == 1) begin
        // master output is same width; direct transfer with no splitting/merging
        m_axi_wdata_int = s_axi_wdata;
        m_axi_wstrb_int = s_axi_wstrb;
        m_axi_wlast_int = s_axi_wlast;
        m_axi_wuser_int = s_axi_wuser;
        m_axi_wvalid_int = 1'b0;

        case (state_reg)
            STATE_IDLE: begin
                // idle state; wait for new burst
                s_axi_awready_next = !m_axi_awvalid;

                if (s_axi_awready && s_axi_awvalid) begin
                    s_axi_awready_next = 1'b0;
                    id_next = s_axi_awid;
                    m_axi_awid_next = s_axi_awid;
                    m_axi_awaddr_next = s_axi_awaddr;
                    m_axi_awlen_next = s_axi_awlen;
                    m_axi_awsize_next = s_axi_awsize;
                    m_axi_awburst_next = s_axi_awburst;
                    m_axi_awlock_next = s_axi_awlock;
                    m_axi_awcache_next = s_axi_awcache;
                    m_axi_awprot_next = s_axi_awprot;
                    m_axi_awqos_next = s_axi_awqos;
                    m_axi_awregion_next = s_axi_awregion;
                    m_axi_awuser_next = s_axi_awuser;
                    m_axi_awvalid_next = 1'b1;
                    s_axi_wready_next = m_axi_wready_int_early;
                    state_next = STATE_DATA;
                end else begin
                    state_next = STATE_IDLE;
                end
            end
            STATE_DATA: begin
                // data state; transfer write data
                s_axi_wready_next = m_axi_wready_int_early;

                if (s_axi_wready && s_axi_wvalid) begin
                    m_axi_wdata_int = s_axi_wdata;
                    m_axi_wstrb_int = s_axi_wstrb;
                    m_axi_wlast_int = s_axi_wlast;
                    m_axi_wuser_int = s_axi_wuser;
                    m_axi_wvalid_int = 1'b1;
                    if (s_axi_wlast) begin
                        // last data word, wait for response
                        s_axi_wready_next = 1'b0;
                        m_axi_bready_next = !s_axi_bvalid;
                        state_next = STATE_RESP;
                    end else begin
                        state_next = STATE_DATA;
                    end
                end else begin
                    state_next = STATE_DATA;
                end
            end
            STATE_RESP: begin
                // resp state; transfer write response
                m_axi_bready_next = !s_axi_bvalid;

                if (m_axi_bready && m_axi_bvalid) begin
                    m_axi_bready_next = 1'b0;
                    s_axi_bid_next = id_reg;
                    s_axi_bresp_next = m_axi_bresp;
                    s_axi_buser_next = m_axi_buser;
                    s_axi_bvalid_next = 1'b1;
                    s_axi_awready_next = !m_axi_awvalid;
                    state_next = STATE_IDLE;
                end else begin
                    state_next = STATE_RESP;
                end
            end
        endcase
    end else if (EXPAND) begin
        // master output is wider; merge writes
        m_axi_wdata_int = {(M_WORD_WIDTH/S_WORD_WIDTH){s_axi_wdata}};
        m_axi_wstrb_int = s_axi_wstrb;
        m_axi_wlast_int = s_axi_wlast;
        m_axi_wuser_int = s_axi_wuser;
        m_axi_wvalid_int = 1'b0;

        case (state_reg)
            STATE_IDLE: begin
                // idle state; wait for new burst
                s_axi_awready_next = !m_axi_awvalid;

                data_next = {DATA_WIDTH{1'b0}};
                strb_next = {STRB_WIDTH{1'b0}};

                if (s_axi_awready && s_axi_awvalid) begin
                    s_axi_awready_next = 1'b0;
                    id_next = s_axi_awid;
                    m_axi_awid_next = s_axi_awid;
                    m_axi_awaddr_next = s_axi_awaddr;
                    addr_next = s_axi_awaddr;
                    burst_next = s_axi_awlen;
                    burst_size_next = s_axi_awsize;
                    if (CONVERT_BURST && s_axi_awcache[1] && (CONVERT_NARROW_BURST || s_axi_awsize == S_BURST_SIZE)) begin
                        // merge writes
                        // require CONVERT_BURST and awcache[1] set
                        master_burst_size_next = M_BURST_SIZE;
                        if (CONVERT_NARROW_BURST) begin
                            m_axi_awlen_next = (({{S_ADDR_BIT_OFFSET+1{1'b0}}, s_axi_awlen} << s_axi_awsize) + s_axi_awaddr[M_ADDR_BIT_OFFSET-1:0]) >> M_BURST_SIZE;
                        end else begin
                            m_axi_awlen_next = ({1'b0, s_axi_awlen} + s_axi_awaddr[M_ADDR_BIT_OFFSET-1:S_ADDR_BIT_OFFSET]) >> $clog2(SEGMENT_COUNT);
                        end
                        m_axi_awsize_next = M_BURST_SIZE;
                        state_next = STATE_DATA_2;
                    end else begin
                        // output narrow burst
                        master_burst_size_next = s_axi_awsize;
                        m_axi_awlen_next = s_axi_awlen;
                        m_axi_awsize_next = s_axi_awsize;
                        state_next = STATE_DATA;
                    end
                    m_axi_awburst_next = s_axi_awburst;
                    m_axi_awlock_next = s_axi_awlock;
                    m_axi_awcache_next = s_axi_awcache;
                    m_axi_awprot_next = s_axi_awprot;
                    m_axi_awqos_next = s_axi_awqos;
                    m_axi_awregion_next = s_axi_awregion;
                    m_axi_awuser_next = s_axi_awuser;
                    m_axi_awvalid_next = 1'b1;
                    s_axi_wready_next = m_axi_wready_int_early;
                end else begin
                    state_next = STATE_IDLE;
                end
            end
            STATE_DATA: begin
                // data state; transfer write data
                s_axi_wready_next = m_axi_wready_int_early;

                if (s_axi_wready && s_axi_wvalid) begin
                    m_axi_wdata_int = {(M_WORD_WIDTH/S_WORD_WIDTH){s_axi_wdata}};
                    m_axi_wstrb_int = s_axi_wstrb << (addr_reg[M_ADDR_BIT_OFFSET-1:S_ADDR_BIT_OFFSET] * S_STRB_WIDTH);
                    m_axi_wlast_int = s_axi_wlast;
                    m_axi_wuser_int = s_axi_wuser;
                    m_axi_wvalid_int = 1'b1;
                    addr_next = addr_reg + (1 << burst_size_reg);
                    if (s_axi_wlast) begin
                        s_axi_wready_next = 1'b0;
                        m_axi_bready_next = !s_axi_bvalid;
                        state_next = STATE_RESP;
                    end else begin
                        state_next = STATE_DATA;
                    end
                end else begin
                    state_next = STATE_DATA;
                end
            end
            STATE_DATA_2: begin
                s_axi_wready_next = m_axi_wready_int_early;

                if (s_axi_wready && s_axi_wvalid) begin
                    if (CONVERT_NARROW_BURST) begin
                        for (i = 0; i < S_WORD_WIDTH; i = i + 1) begin
                            if (s_axi_wstrb[i]) begin
                                data_next[addr_reg[M_ADDR_BIT_OFFSET-1:S_ADDR_BIT_OFFSET]*SEGMENT_DATA_WIDTH+i*M_WORD_SIZE +: M_WORD_SIZE] = s_axi_wdata[i*M_WORD_SIZE +: M_WORD_SIZE];
                                strb_next[addr_reg[M_ADDR_BIT_OFFSET-1:S_ADDR_BIT_OFFSET]*SEGMENT_STRB_WIDTH+i] = 1'b1;
                            end
                        end
                    end else begin
                        data_next[addr_reg[M_ADDR_BIT_OFFSET-1:S_ADDR_BIT_OFFSET]*SEGMENT_DATA_WIDTH +: SEGMENT_DATA_WIDTH] = s_axi_wdata;
                        strb_next[addr_reg[M_ADDR_BIT_OFFSET-1:S_ADDR_BIT_OFFSET]*SEGMENT_STRB_WIDTH +: SEGMENT_STRB_WIDTH] = s_axi_wstrb;
                    end
                    m_axi_wdata_int = data_next;
                    m_axi_wstrb_int = strb_next;
                    m_axi_wlast_int = s_axi_wlast;
                    m_axi_wuser_int = s_axi_wuser;
                    burst_next = burst_reg - 1;
                    addr_next = addr_reg + (1 << burst_size_reg);
                    if (addr_next[master_burst_size_reg] != addr_reg[master_burst_size_reg]) begin
                        data_next = {DATA_WIDTH{1'b0}};
                        strb_next = {STRB_WIDTH{1'b0}};
                        m_axi_wvalid_int = 1'b1;
                    end
                    if (burst_reg == 0) begin
                        m_axi_wvalid_int = 1'b1;
                        s_axi_wready_next = 1'b0;
                        m_axi_bready_next = !s_axi_bvalid;
                        state_next = STATE_RESP;
                    end else begin
                        state_next = STATE_DATA_2;
                    end
                end else begin
                    state_next = STATE_DATA_2;
                end
            end
            STATE_RESP: begin
                // resp state; transfer write response
                m_axi_bready_next = !s_axi_bvalid;

                if (m_axi_bready && m_axi_bvalid) begin
                    m_axi_bready_next = 1'b0;
                    s_axi_bid_next = id_reg;
                    s_axi_bresp_next = m_axi_bresp;
                    s_axi_buser_next = m_axi_buser;
                    s_axi_bvalid_next = 1'b1;
                    s_axi_awready_next = !m_axi_awvalid;
                    state_next = STATE_IDLE;
                end else begin
                    state_next = STATE_RESP;
                end
            end
        endcase
    end else begin
        // master output is narrower; split writes, and possibly split burst
        m_axi_wdata_int = data_reg;
        m_axi_wstrb_int = strb_reg;
        m_axi_wlast_int = 1'b0;
        m_axi_wuser_int = wuser_reg;
        m_axi_wvalid_int = 1'b0;

        case (state_reg)
            STATE_IDLE: begin
                // idle state; wait for new burst
                s_axi_awready_next = !m_axi_awvalid;

                first_transfer_next = 1'b1;

                if (s_axi_awready && s_axi_awvalid) begin
                    s_axi_awready_next = 1'b0;
                    id_next = s_axi_awid;
                    m_axi_awid_next = s_axi_awid;
                    m_axi_awaddr_next = s_axi_awaddr;
                    addr_next = s_axi_awaddr;
                    burst_next = s_axi_awlen;
                    burst_size_next = s_axi_awsize;
                    burst_active_next = 1'b1;
                    if (s_axi_awsize > M_BURST_SIZE) begin
                        // need to adjust burst size
                        if (s_axi_awlen >> (8+M_BURST_SIZE-s_axi_awsize) != 0) begin
                            // limit burst length to max
                            master_burst_next = (8'd255 << (s_axi_awsize-M_BURST_SIZE)) | ((~s_axi_awaddr & (8'hff >> (8-s_axi_awsize))) >> M_BURST_SIZE);
                        end else begin
                            master_burst_next = (s_axi_awlen << (s_axi_awsize-M_BURST_SIZE)) | ((~s_axi_awaddr & (8'hff >> (8-s_axi_awsize))) >> M_BURST_SIZE);
                        end
                        master_burst_size_next = M_BURST_SIZE;
                        m_axi_awlen_next = master_burst_next;
                        m_axi_awsize_next = master_burst_size_next;
                    end else begin
                        // pass through narrow (enough) burst
                        master_burst_next = s_axi_awlen;
                        master_burst_size_next = s_axi_awsize;
                        m_axi_awlen_next = s_axi_awlen;
                        m_axi_awsize_next = s_axi_awsize;
                    end
                    m_axi_awburst_next = s_axi_awburst;
                    m_axi_awlock_next = s_axi_awlock;
                    m_axi_awcache_next = s_axi_awcache;
                    m_axi_awprot_next = s_axi_awprot;
                    m_axi_awqos_next = s_axi_awqos;
                    m_axi_awregion_next = s_axi_awregion;
                    m_axi_awuser_next = s_axi_awuser;
                    m_axi_awvalid_next = 1'b1;
                    s_axi_wready_next = m_axi_wready_int_early;
                    state_next = STATE_DATA;
                end else begin
                    state_next = STATE_IDLE;
                end
            end
            STATE_DATA: begin
                s_axi_wready_next = m_axi_wready_int_early;

                if (s_axi_wready && s_axi_wvalid) begin
                    data_next = s_axi_wdata;
                    strb_next = s_axi_wstrb;
                    wuser_next = s_axi_wuser;
                    m_axi_wdata_int = s_axi_wdata >> (addr_reg[S_ADDR_BIT_OFFSET-1:M_ADDR_BIT_OFFSET] * M_DATA_WIDTH);
                    m_axi_wstrb_int = s_axi_wstrb >> (addr_reg[S_ADDR_BIT_OFFSET-1:M_ADDR_BIT_OFFSET] * M_STRB_WIDTH);
                    m_axi_wlast_int = 1'b0;
                    m_axi_wuser_int = s_axi_wuser;
                    m_axi_wvalid_int = 1'b1;
                    burst_next = burst_reg - 1;
                    burst_active_next = burst_reg != 0;
                    master_burst_next = master_burst_reg - 1;
                    addr_next = (addr_reg + (1 << master_burst_size_reg)) & ({ADDR_WIDTH{1'b1}} << master_burst_size_reg);
                    if (master_burst_reg == 0) begin
                        s_axi_wready_next = 1'b0;
                        m_axi_bready_next = !s_axi_bvalid && !s_axi_awvalid;
                        m_axi_wlast_int = 1'b1;
                        state_next = STATE_RESP;
                    end else if (addr_next[burst_size_reg] != addr_reg[burst_size_reg]) begin
                        state_next = STATE_DATA;
                    end else begin
                        s_axi_wready_next = 1'b0;
                        state_next = STATE_DATA_2;
                    end
                end else begin
                    state_next = STATE_DATA;
                end
            end
            STATE_DATA_2: begin
                s_axi_wready_next = 1'b0;

                if (m_axi_wready_int_reg) begin
                    m_axi_wdata_int = data_reg >> (addr_reg[S_ADDR_BIT_OFFSET-1:M_ADDR_BIT_OFFSET] * M_DATA_WIDTH);
                    m_axi_wstrb_int = strb_reg >> (addr_reg[S_ADDR_BIT_OFFSET-1:M_ADDR_BIT_OFFSET] * M_STRB_WIDTH);
                    m_axi_wlast_int = 1'b0;
                    m_axi_wuser_int = wuser_reg;
                    m_axi_wvalid_int = 1'b1;
                    master_burst_next = master_burst_reg - 1;
                    addr_next = (addr_reg + (1 << master_burst_size_reg)) & ({ADDR_WIDTH{1'b1}} << master_burst_size_reg);
                    if (master_burst_reg == 0) begin
                        // burst on master interface finished; transfer response
                        s_axi_wready_next = 1'b0;
                        m_axi_bready_next = !s_axi_bvalid && !m_axi_awvalid;
                        m_axi_wlast_int = 1'b1;
                        state_next = STATE_RESP;
                    end else if (addr_next[burst_size_reg] != addr_reg[burst_size_reg]) begin
                        state_next = STATE_DATA;
                    end else begin
                        s_axi_wready_next = 1'b0;
                        state_next = STATE_DATA_2;
                    end
                end else begin
                    state_next = STATE_DATA_2;
                end
            end
            STATE_RESP: begin
                // resp state; transfer write response
                m_axi_bready_next = !s_axi_bvalid && !m_axi_awvalid;

                if (m_axi_bready && m_axi_bvalid) begin
                    first_transfer_next = 1'b0;
                    m_axi_bready_next = 1'b0;
                    s_axi_bid_next = id_reg;
                    if (first_transfer_reg || m_axi_bresp != 0) begin
                        s_axi_bresp_next = m_axi_bresp;
                    end

                    if (burst_reg >> (8+M_BURST_SIZE-burst_size_reg) != 0) begin
                        // limit burst length to max
                        master_burst_next = 8'd255;
                    end else begin
                        master_burst_next = (burst_reg << (burst_size_reg-M_BURST_SIZE)) | (8'hff >> (8-burst_size_reg) >> M_BURST_SIZE);
                    end
                    master_burst_size_next = M_BURST_SIZE;
                    m_axi_awaddr_next = addr_reg;
                    m_axi_awlen_next = master_burst_next;
                    m_axi_awsize_next = master_burst_size_next;
                    if (burst_active_reg) begin
                        // burst on slave interface still active; start new burst
                        m_axi_awvalid_next = 1'b1;
                        state_next = STATE_DATA;
                    end else begin
                        // burst on slave interface finished; return to idle
                        s_axi_bvalid_next = 1'b1;
                        s_axi_awready_next = !m_axi_awvalid;
                        state_next = STATE_IDLE;
                    end
                end else begin
                    state_next = STATE_RESP;
                end
            end
        endcase
    end
end

always @(posedge clk) begin
    state_reg <= state_next;

    id_reg <= id_next;
    addr_reg <= addr_next;
    data_reg <= data_next;
    strb_reg <= strb_next;
    wuser_reg <= wuser_next;
    burst_reg <= burst_next;
    burst_size_reg <= burst_size_next;
    master_burst_reg <= master_burst_next;
    master_burst_size_reg <= master_burst_size_next;
    burst_active_reg <= burst_active_next;
    first_transfer_reg <= first_transfer_next;

    s_axi_awready_reg <= s_axi_awready_next;
    s_axi_wready_reg <= s_axi_wready_next;
    s_axi_bid_reg <= s_axi_bid_next;
    s_axi_bresp_reg <= s_axi_bresp_next;
    s_axi_buser_reg <= s_axi_buser_next;
    s_axi_bvalid_reg <= s_axi_bvalid_next;

    m_axi_awid_reg <= m_axi_awid_next;
    m_axi_awaddr_reg <= m_axi_awaddr_next;
    m_axi_awlen_reg <= m_axi_awlen_next;
    m_axi_awsize_reg <= m_axi_awsize_next;
    m_axi_awburst_reg <= m_axi_awburst_next;
    m_axi_awlock_reg <= m_axi_awlock_next;
    m_axi_awcache_reg <= m_axi_awcache_next;
    m_axi_awprot_reg <= m_axi_awprot_next;
    m_axi_awqos_reg <= m_axi_awqos_next;
    m_axi_awregion_reg <= m_axi_awregion_next;
    m_axi_awuser_reg <= m_axi_awuser_next;
    m_axi_awvalid_reg <= m_axi_awvalid_next;
    m_axi_bready_reg <= m_axi_bready_next;

    if (rst) begin
        state_reg <= STATE_IDLE;

        s_axi_awready_reg <= 1'b0;
        s_axi_wready_reg <= 1'b0;
        s_axi_bvalid_reg <= 1'b0;

        m_axi_awvalid_reg <= 1'b0;
        m_axi_bready_reg <= 1'b0;
    end
end

// output datapath logic
reg [M_DATA_WIDTH-1:0] m_axi_wdata_reg  = {M_DATA_WIDTH{1'b0}};
reg [M_STRB_WIDTH-1:0] m_axi_wstrb_reg  = {M_STRB_WIDTH{1'b0}};
reg                    m_axi_wlast_reg  = 1'b0;
reg [WUSER_WIDTH-1:0]  m_axi_wuser_reg  = 1'b0;
reg                    m_axi_wvalid_reg = 1'b0, m_axi_wvalid_next;

reg [M_DATA_WIDTH-1:0] temp_m_axi_wdata_reg  = {M_DATA_WIDTH{1'b0}};
reg [M_STRB_WIDTH-1:0] temp_m_axi_wstrb_reg  = {M_STRB_WIDTH{1'b0}};
reg                    temp_m_axi_wlast_reg  = 1'b0;
reg [WUSER_WIDTH-1:0]  temp_m_axi_wuser_reg  = 1'b0;
reg                    temp_m_axi_wvalid_reg = 1'b0, temp_m_axi_wvalid_next;

// datapath control
reg store_axi_w_int_to_output;
reg store_axi_w_int_to_temp;
reg store_axi_w_temp_to_output;

assign m_axi_wdata  = m_axi_wdata_reg;
assign m_axi_wstrb  = m_axi_wstrb_reg;
assign m_axi_wlast  = m_axi_wlast_reg;
assign m_axi_wuser  = WUSER_ENABLE ? m_axi_wuser_reg : {WUSER_WIDTH{1'b0}};
assign m_axi_wvalid = m_axi_wvalid_reg;

// enable ready input next cycle if output is ready or the temp reg will not be filled on the next cycle (output reg empty or no input)
assign m_axi_wready_int_early = m_axi_wready | (~temp_m_axi_wvalid_reg & (~m_axi_wvalid_reg | ~m_axi_wvalid_int));

always @* begin
    // transfer sink ready state to source
    m_axi_wvalid_next = m_axi_wvalid_reg;
    temp_m_axi_wvalid_next = temp_m_axi_wvalid_reg;

    store_axi_w_int_to_output = 1'b0;
    store_axi_w_int_to_temp = 1'b0;
    store_axi_w_temp_to_output = 1'b0;

    if (m_axi_wready_int_reg) begin
        // input is ready
        if (m_axi_wready | ~m_axi_wvalid_reg) begin
            // output is ready or currently not valid, transfer data to output
            m_axi_wvalid_next = m_axi_wvalid_int;
            store_axi_w_int_to_output = 1'b1;
        end else begin
            // output is not ready, store input in temp
            temp_m_axi_wvalid_next = m_axi_wvalid_int;
            store_axi_w_int_to_temp = 1'b1;
        end
    end else if (m_axi_wready) begin
        // input is not ready, but output is ready
        m_axi_wvalid_next = temp_m_axi_wvalid_reg;
        temp_m_axi_wvalid_next = 1'b0;
        store_axi_w_temp_to_output = 1'b1;
    end
end

always @(posedge clk) begin
    if (rst) begin
        m_axi_wvalid_reg <= 1'b0;
        m_axi_wready_int_reg <= 1'b0;
        temp_m_axi_wvalid_reg <= 1'b0;
    end else begin
        m_axi_wvalid_reg <= m_axi_wvalid_next;
        m_axi_wready_int_reg <= m_axi_wready_int_early;
        temp_m_axi_wvalid_reg <= temp_m_axi_wvalid_next;
    end

    // datapath
    if (store_axi_w_int_to_output) begin
        m_axi_wdata_reg <= m_axi_wdata_int;
        m_axi_wstrb_reg <= m_axi_wstrb_int;
        m_axi_wlast_reg <= m_axi_wlast_int;
        m_axi_wuser_reg <= m_axi_wuser_int;
    end else if (store_axi_w_temp_to_output) begin
        m_axi_wdata_reg <= temp_m_axi_wdata_reg;
        m_axi_wstrb_reg <= temp_m_axi_wstrb_reg;
        m_axi_wlast_reg <= temp_m_axi_wlast_reg;
        m_axi_wuser_reg <= temp_m_axi_wuser_reg;
    end

    if (store_axi_w_int_to_temp) begin
        temp_m_axi_wdata_reg <= m_axi_wdata_int;
        temp_m_axi_wstrb_reg <= m_axi_wstrb_int;
        temp_m_axi_wlast_reg <= m_axi_wlast_int;
        temp_m_axi_wuser_reg <= m_axi_wuser_int;
    end
end

endmodule