axi_pkg.sv

// Copyright (c) 2014-2020 ETH Zurich, University of Bologna
//
// Copyright and related rights are licensed under the Solderpad Hardware
// License, Version 0.51 (the "License"); you may not use this file except in
// compliance with the License.  You may obtain a copy of the License at
// http://solderpad.org/licenses/SHL-0.51. Unless required by applicable law
// or agreed to in writing, software, hardware and materials distributed under
// this License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
// CONDITIONS OF ANY KIND, either express or implied. See the License for the
// specific language governing permissions and limitations under the License.
//
// Authors:
// - Andreas Kurth <akurth@iis.ee.ethz.ch>
// - Florian Zaruba <zarubaf@iis.ee.ethz.ch>
// - Wolfgang Roenninger <wroennin@iis.ee.ethz.ch>
// - Fabian Schuiki <fschuiki@iis.ee.ethz.ch>
// - Matheus Cavalcante <matheusd@iis.ee.ethz.ch>

//! AXI Package
/// Contains all necessary type definitions, constants, and generally useful functions.
package axi_pkg;
    /// AXI Transaction Burst Width.
  parameter int unsigned BurstWidth  = 32'd2;
  /// AXI Transaction Response Width.
  parameter int unsigned RespWidth   = 32'd2;
  /// AXI Transaction Cacheability Width.
  parameter int unsigned CacheWidth  = 32'd4;
  /// AXI Transaction Protection Width.
  parameter int unsigned ProtWidth   = 32'd3;
  /// AXI Transaction Quality of Service Width.
  parameter int unsigned QosWidth    = 32'd4;
  /// AXI Transaction Region Width.
  parameter int unsigned RegionWidth = 32'd4;
  /// AXI Transaction Length Width.
  parameter int unsigned LenWidth    = 32'd8;
  /// AXI Transaction Size Width.
  parameter int unsigned SizeWidth   = 32'd3;
  /// AXI Lock Width.
  parameter int unsigned LockWidth   = 32'd1;
  /// AXI5 Atomic Operation Width.
  parameter int unsigned AtopWidth   = 32'd6;
  /// AXI5 Non-Secure Address Identifier.
  parameter int unsigned NsaidWidth  = 32'd4;

  /// AXI Transaction Burst Width.
  typedef logic [1:0]  burst_t;
  /// AXI Transaction Response Type.
  typedef logic [1:0]   resp_t;
  /// AXI Transaction Cacheability Type.
  typedef logic [3:0]  cache_t;
  /// AXI Transaction Protection Type.
  typedef logic [2:0]   prot_t;
  /// AXI Transaction Quality of Service Type.
  typedef logic [3:0]    qos_t;
  /// AXI Transaction Region Type.
  typedef logic [3:0] region_t;
  /// AXI Transaction Length Type.
  typedef logic [7:0]    len_t;
  /// AXI Transaction Size Type.
  typedef logic [2:0]   size_t;
  /// AXI5 Atomic Operation Type.
  typedef logic [5:0]   atop_t; // atomic operations
  /// AXI5 Non-Secure Address Identifier.
  typedef logic [3:0]  nsaid_t;

  /// In a fixed burst:
  /// - The address is the same for every transfer in the burst.
  /// - The byte lanes that are valid are constant for all beats in the burst.  However, within
  ///   those byte lanes, the actual bytes that have `wstrb` asserted can differ for each beat in
  ///   the burst.
  /// This burst type is used for repeated accesses to the same location such as when loading or
  /// emptying a FIFO.
  localparam BURST_FIXED = 2'b00;
  /// In an incrementing burst, the address for each transfer in the burst is an increment of the
  /// address for the previous transfer.  The increment value depends on the size of the transfer.
  /// For example, the address for each transfer in a burst with a size of 4 bytes is the previous
  /// address plus four.
  /// This burst type is used for accesses to normal sequential memory.
  localparam BURST_INCR  = 2'b01;
  /// A wrapping burst is similar to an incrementing burst, except that the address wraps around to
  /// a lower address if an upper address limit is reached.
  /// The following restrictions apply to wrapping bursts:
  /// - The start address must be aligned to the size of each transfer.
  /// - The length of the burst must be 2, 4, 8, or 16 transfers.
  localparam BURST_WRAP  = 2'b10;

  /// Normal access success.  Indicates that a normal access has been successful. Can also indicate
  /// that an exclusive access has failed.
  localparam RESP_OKAY   = 2'b00;
  /// Exclusive access okay.  Indicates that either the read or write portion of an exclusive access
  /// has been successful.
  localparam RESP_EXOKAY = 2'b01;
  /// Slave error.  Used when the access has reached the slave successfully, but the slave wishes to
  /// return an error condition to the originating master.
  localparam RESP_SLVERR = 2'b10;
  /// Decode error.  Generated, typically by an interconnect component, to indicate that there is no
  /// slave at the transaction address.
  localparam RESP_DECERR = 2'b11;

  /// When this bit is asserted, the interconnect, or any component, can delay the transaction
  /// reaching its final destination for any number of cycles.
  localparam CACHE_BUFFERABLE = 4'b0001;
  /// When HIGH, Modifiable indicates that the characteristics of the transaction can be modified.
  /// When Modifiable is LOW, the transaction is Non-modifiable.
  localparam CACHE_MODIFIABLE = 4'b0010;
  /// When this bit is asserted, read allocation of the transaction is recommended but is not
  /// mandatory.
  localparam CACHE_RD_ALLOC   = 4'b0100;
  /// When this bit is asserted, write allocation of the transaction is recommended but is not
  /// mandatory.
  localparam CACHE_WR_ALLOC   = 4'b1000;

  /// Maximum number of bytes per burst, as specified by `size` (see Table A3-2).
  function automatic shortint unsigned num_bytes(size_t size);
    return 1 << size;
  endfunction

  /// An overly long address type.
  /// It lets us define functions that work generically for shorter addresses.  We rely on the
  /// synthesizer to optimize the unused bits away.
  typedef logic [127:0] largest_addr_t;

  /// Aligned address of burst (see A3-51).
  function automatic largest_addr_t aligned_addr(largest_addr_t addr, size_t size);
    return (addr >> size) << size;
  endfunction

  /// Warp boundary of a `BURST_WRAP` transfer (see A3-51).
  /// This is the lowest address accessed within a wrapping burst.
  /// This address is aligned to the size and length of the burst.
  /// The length of a `BURST_WRAP` has to be 2, 4, 8, or 16 transfers.
  function automatic largest_addr_t wrap_boundary (largest_addr_t addr, size_t size, len_t len);
    largest_addr_t wrap_addr;

    // pragma translate_off
    `ifndef VERILATOR
      assume (len == len_t'(4'b1) || len == len_t'(4'b11) || len == len_t'(4'b111) ||
          len == len_t'(4'b1111)) else
        $error("AXI BURST_WRAP with not allowed len of: %0h", len);
    `endif
    // pragma translate_on

    // In A3-51 the wrap boundary is defined as:
    // `Wrap_Boundary = (INT(Start_Address / (Number_Bytes × Burst_Length))) ×
    //    (Number_Bytes × Burst_Length)`
    // Whereas the aligned address is defined as:
    // `Aligned_Address = (INT(Start_Address / Number_Bytes)) × Number_Bytes`
    // This leads to the wrap boundary using the same calculation as the aligned address, difference
    // being the additional dependency on the burst length. The addition in the case statement
    // is equal to the multiplication with `Burst_Length` as a shift (used by `aligned_addr`) is
    // equivalent with multiplication and division by a power of two, which conveniently are the
    // only allowed values for `len` of a `BURST_WRAP`.
    unique case (len)
      4'b1    : wrap_addr = (addr >> (unsigned'(size) + 1)) << (unsigned'(size) + 1); // multiply `Number_Bytes` by `2`
      4'b11   : wrap_addr = (addr >> (unsigned'(size) + 2)) << (unsigned'(size) + 2); // multiply `Number_Bytes` by `4`
      4'b111  : wrap_addr = (addr >> (unsigned'(size) + 3)) << (unsigned'(size) + 3); // multiply `Number_Bytes` by `8`
      4'b1111 : wrap_addr = (addr >> (unsigned'(size) + 4)) << (unsigned'(size) + 4); // multiply `Number_Bytes` by `16`
      default : wrap_addr = '0;
    endcase
    return wrap_addr;
  endfunction

  /// Address of beat (see A3-51).
  function automatic largest_addr_t
  beat_addr(largest_addr_t addr, size_t size, len_t len, burst_t burst, shortint unsigned i_beat);
    largest_addr_t ret_addr = addr;
    largest_addr_t wrp_bond = '0;
    if (burst == BURST_WRAP) begin
      // do not trigger the function if there is no wrapping burst, to prevent assumptions firing
      wrp_bond = wrap_boundary(addr, size, len);
    end
    if (i_beat != 0 && burst != BURST_FIXED) begin
      // From A3-51:
      // For an INCR burst, and for a WRAP burst for which the address has not wrapped, this
      // equation determines the address of any transfer after the first transfer in a burst:
      // `Address_N = Aligned_Address + (N – 1) × Number_Bytes` (N counts from 1 to len!)
      ret_addr = aligned_addr(addr, size) + i_beat * num_bytes(size);
      // From A3-51:
      // For a WRAP burst, if Address_N = Wrap_Boundary + (Number_Bytes × Burst_Length), then:
      // * Use this equation for the current transfer:
      //     `Address_N = Wrap_Boundary`
      // * Use this equation for any subsequent transfers:
      //     `Address_N = Start_Address + ((N – 1) × Number_Bytes) – (Number_Bytes × Burst_Length)`
      // This means that the address calculation of a `BURST_WRAP` fundamentally works the same
      // as for a `BURST_INC`, the difference is when the calculated address increments
      // over the wrap threshold, the address wraps around by subtracting the accessed address
      // space from the normal `BURST_INCR` address. The lower wrap boundary is equivalent to
      // The wrap trigger condition minus the container size (`num_bytes(size) * (len + 1)`).
      if (burst == BURST_WRAP && ret_addr >= wrp_bond + (num_bytes(size) * (len + 1))) begin
        ret_addr = ret_addr - (num_bytes(size) * (len + 1));
      end
    end
    return ret_addr;
  endfunction

  /// Index of lowest byte in beat (see A3-51).
  function automatic shortint unsigned
  beat_lower_byte(largest_addr_t addr, size_t size, len_t len, burst_t burst,
      shortint unsigned strobe_width, shortint unsigned i_beat);
    largest_addr_t _addr = beat_addr(addr, size, len, burst, i_beat);
    return shortint'(_addr - (_addr / strobe_width) * strobe_width);
  endfunction

  /// Index of highest byte in beat (see A3-51).
  function automatic shortint unsigned
  beat_upper_byte(largest_addr_t addr, size_t size, len_t len, burst_t burst,
      shortint unsigned strobe_width, shortint unsigned i_beat);
    if (i_beat == 0) begin
      return aligned_addr(addr, size) + (num_bytes(size) - 1) - (addr / strobe_width) * strobe_width;
    end else begin
      return beat_lower_byte(addr, size, len, burst, strobe_width, i_beat) + num_bytes(size) - 1;
    end
  endfunction

  /// Is the bufferable bit set?
  function automatic logic bufferable(cache_t cache);
    return |(cache & CACHE_BUFFERABLE);
  endfunction

  /// Is the modifiable bit set?
  function automatic logic modifiable(cache_t cache);
    return |(cache & CACHE_MODIFIABLE);
  endfunction

  /// Memory Type.
  typedef enum logic [3:0] {
    DEVICE_NONBUFFERABLE,
    DEVICE_BUFFERABLE,
    NORMAL_NONCACHEABLE_NONBUFFERABLE,
    NORMAL_NONCACHEABLE_BUFFERABLE,
    WTHRU_NOALLOCATE,
    WTHRU_RALLOCATE,
    WTHRU_WALLOCATE,
    WTHRU_RWALLOCATE,
    WBACK_NOALLOCATE,
    WBACK_RALLOCATE,
    WBACK_WALLOCATE,
    WBACK_RWALLOCATE
  } mem_type_t;

  /// Create an `AR_CACHE` field from a `mem_type_t` type.
  function automatic logic [3:0] get_arcache(mem_type_t mtype);
    unique case (mtype)
      DEVICE_NONBUFFERABLE              : return 4'b0000;
      DEVICE_BUFFERABLE                 : return 4'b0001;
      NORMAL_NONCACHEABLE_NONBUFFERABLE : return 4'b0010;
      NORMAL_NONCACHEABLE_BUFFERABLE    : return 4'b0011;
      WTHRU_NOALLOCATE                  : return 4'b1010;
      WTHRU_RALLOCATE                   : return 4'b1110;
      WTHRU_WALLOCATE                   : return 4'b1010;
      WTHRU_RWALLOCATE                  : return 4'b1110;
      WBACK_NOALLOCATE                  : return 4'b1011;
      WBACK_RALLOCATE                   : return 4'b1111;
      WBACK_WALLOCATE                   : return 4'b1011;
      WBACK_RWALLOCATE                  : return 4'b1111;
    endcase // mtype
  endfunction

  /// Create an `AW_CACHE` field from a `mem_type_t` type.
  function automatic logic [3:0] get_awcache(mem_type_t mtype);
    unique case (mtype)
      DEVICE_NONBUFFERABLE              : return 4'b0000;
      DEVICE_BUFFERABLE                 : return 4'b0001;
      NORMAL_NONCACHEABLE_NONBUFFERABLE : return 4'b0010;
      NORMAL_NONCACHEABLE_BUFFERABLE    : return 4'b0011;
      WTHRU_NOALLOCATE                  : return 4'b0110;
      WTHRU_RALLOCATE                   : return 4'b0110;
      WTHRU_WALLOCATE                   : return 4'b1110;
      WTHRU_RWALLOCATE                  : return 4'b1110;
      WBACK_NOALLOCATE                  : return 4'b0111;
      WBACK_RALLOCATE                   : return 4'b0111;
      WBACK_WALLOCATE                   : return 4'b1111;
      WBACK_RWALLOCATE                  : return 4'b1111;
    endcase // mtype
  endfunction

  /// RESP precedence: DECERR > SLVERR > OKAY > EXOKAY.  This is not defined in the AXI standard but
  /// depends on the implementation.  We consistently use the precedence above.  Rationale:
  /// - EXOKAY means an exclusive access was successful, whereas OKAY means it was not.  Thus, if
  ///   OKAY and EXOKAY are to be merged, OKAY precedes because the exclusive access was not fully
  ///   successful.
  /// - Both DECERR and SLVERR mean (part of) a transaction were unsuccessful, whereas OKAY means an
  ///   entire transaction was successful.  Thus both DECERR and SLVERR precede OKAY.
  /// - DECERR means (part of) a transactions could not be routed to a slave component, whereas
  ///   SLVERR means the transaction reached a slave component but lead to an error condition there.
  ///   Thus DECERR precedes SLVERR because DECERR happens earlier in the handling of a transaction.
  function automatic resp_t resp_precedence(resp_t resp_a, resp_t resp_b);
    unique case (resp_a)
      RESP_OKAY: begin
        // Any response except EXOKAY precedes OKAY.
        if (resp_b == RESP_EXOKAY) begin
          return resp_a;
        end else begin
          return resp_b;
        end
      end
      RESP_EXOKAY: begin
        // Any response precedes EXOKAY.
        return resp_b;
      end
      RESP_SLVERR: begin
        // Only DECERR precedes SLVERR.
        if (resp_b == RESP_DECERR) begin
          return resp_b;
        end else begin
          return resp_a;
        end
      end
      RESP_DECERR: begin
        // No response precedes DECERR.
        return resp_a;
      end
    endcase
  endfunction

  /// AW Width: Returns the width of the AW channel payload
  function automatic int unsigned aw_width(int unsigned addr_width, int unsigned id_width,
                                           int unsigned user_width );
    // Sum the individual bit widths of the signals
    return (id_width + addr_width + LenWidth + SizeWidth + BurstWidth + LockWidth + CacheWidth +
            ProtWidth + QosWidth + RegionWidth + AtopWidth + user_width );
  endfunction

  /// W Width: Returns the width of the W channel payload
  function automatic int unsigned w_width(int unsigned data_width, int unsigned user_width );
    // Sum the individual bit widths of the signals
    return (data_width + data_width / 32'd8 + 32'd1 + user_width);
    //                   ^- StrobeWidth       ^- LastWidth
  endfunction

  /// B Width: Returns the width of the B channel payload
  function automatic int unsigned b_width(int unsigned id_width, int unsigned user_width );
    // Sum the individual bit widths of the signals
    return (id_width + RespWidth + user_width);
  endfunction

  /// AR Width: Returns the width of the AR channel payload
  function automatic int unsigned ar_width(int unsigned addr_width, int unsigned id_width,
                                           int unsigned user_width );
    // Sum the individual bit widths of the signals
    return (id_width + addr_width + LenWidth + SizeWidth + BurstWidth + LockWidth + CacheWidth +
            ProtWidth + QosWidth + RegionWidth + user_width );
  endfunction

  /// R Width: Returns the width of the R channel payload
  function automatic int unsigned r_width(int unsigned data_width, int unsigned id_width,
                                          int unsigned user_width );
    // Sum the individual bit widths of the signals
    return (id_width + data_width + RespWidth + 32'd1 + user_width);
    //                                          ^- LastWidth
  endfunction

  /// Request Width: Returns the width of the request channel
  function automatic int unsigned req_width(int unsigned addr_width,    int unsigned data_width,
                                            int unsigned id_width,      int unsigned aw_user_width,
                                            int unsigned ar_user_width, int unsigned w_user_width   );
    // Sum the individual bit widths of the signals and their handshakes
    //                                                      v- valids
    return (aw_width(addr_width, id_width, aw_user_width) + 32'd1 +
            w_width(data_width, w_user_width)             + 32'd1 +
            ar_width(addr_width, id_width, ar_user_width) + 32'd1 + 32'd1 + 32'd1 );
    //                                                              ^- R,   ^- B ready
  endfunction

  /// Response Width: Returns the width of the response channel
  function automatic int unsigned rsp_width(int unsigned data_width,   int unsigned id_width,
                                            int unsigned r_user_width, int unsigned b_user_width );
    // Sum the individual bit widths of the signals and their handshakes
    //                                                    v- valids
    return (r_width(data_width, id_width, r_user_width) + 32'd1 +
            b_width(id_width, b_user_width)             + 32'd1 + 32'd1 + 32'd1 + 32'd1);
    //                                                            ^- AW,  ^- AR,  ^- W ready
  endfunction

  // ATOP[5:0]
  /// - Sends a single data value with an address.
  /// - The target swaps the value at the addressed location with the data value that is supplied in
  ///   the transaction.
  /// - The original data value at the addressed location is returned.
  /// - Outbound data size is 1, 2, 4, or 8 bytes.
  /// - Inbound data size is the same as the outbound data size.
  localparam ATOP_ATOMICSWAP  = 6'b110000;
  /// - Sends two data values, the compare value and the swap value, to the addressed location.
  ///   The compare and swap values are of equal size.
  /// - The data value at the addressed location is checked against the compare value:
  ///   - If the values match, the swap value is written to the addressed location.
  ///   - If the values do not match, the swap value is not written to the addressed location.
  /// - The original data value at the addressed location is returned.
  /// - Outbound data size is 2, 4, 8, 16, or 32 bytes.
  /// - Inbound data size is half of the outbound data size because the outbound data contains both
  ///   compare and swap values, whereas the inbound data has only the original data value.
  localparam ATOP_ATOMICCMP   = 6'b110001;
  // ATOP[5:4]
  /// Perform no atomic operation.
  localparam ATOP_NONE        = 2'b00;
  /// - Sends a single data value with an address and the atomic operation to be performed.
  /// - The target performs the operation using the sent data and value at the addressed location as
  ///   operands.
  /// - The result is stored in the address location.
  /// - A single response is given without data.
  /// - Outbound data size is 1, 2, 4, or 8 bytes.
  localparam ATOP_ATOMICSTORE = 2'b01;
  /// Sends a single data value with an address and the atomic operation to be performed.
  /// - The original data value at the addressed location is returned.
  /// - The target performs the operation using the sent data and value at the addressed location as
  ///   operands.
  /// - The result is stored in the address location.
  /// - Outbound data size is 1, 2, 4, or 8 bytes.
  /// - Inbound data size is the same as the outbound data size.
  localparam ATOP_ATOMICLOAD  = 2'b10;
  // ATOP[3]
  /// For AtomicStore and AtomicLoad transactions `AWATOP[3]` indicates the endianness that is
  /// required for the atomic operation.  The value of `AWATOP[3]` applies to arithmetic operations
  /// only and is ignored for bitwise logical operations.
  /// When deasserted, this bit indicates that the operation is little-endian.
  localparam ATOP_LITTLE_END  = 1'b0;
  /// When asserted, this bit indicates that the operation is big-endian.
  localparam ATOP_BIG_END     = 1'b1;
  // ATOP[2:0]
  /// The value in memory is added to the sent data and the result stored in memory.
  localparam ATOP_ADD   = 3'b000;
  /// Every set bit in the sent data clears the corresponding bit of the data in memory.
  localparam ATOP_CLR   = 3'b001;
  /// Bitwise exclusive OR of the sent data and value in memory.
  localparam ATOP_EOR   = 3'b010;
  /// Every set bit in the sent data sets the corresponding bit of the data in memory.
  localparam ATOP_SET   = 3'b011;
  /// The value stored in memory is the maximum of the existing value and sent data. This operation
  /// assumes signed data.
  localparam ATOP_SMAX  = 3'b100;
  /// The value stored in memory is the minimum of the existing value and sent data. This operation
  /// assumes signed data.
  localparam ATOP_SMIN  = 3'b101;
  /// The value stored in memory is the maximum of the existing value and sent data. This operation
  /// assumes unsigned data.
  localparam ATOP_UMAX  = 3'b110;
  /// The value stored in memory is the minimum of the existing value and sent data. This operation
  /// assumes unsigned data.
  localparam ATOP_UMIN  = 3'b111;
  // ATOP[5] == 1'b1 indicated that an atomic transaction has a read response
  // Ussage eg: if (req_i.aw.atop[axi_pkg::ATOP_R_RESP]) begin
  localparam ATOP_R_RESP = 32'd5;

  // `xbar_latency_e` and `xbar_cfg_t` are documented in `doc/axi_xbar.md`.
  /// Slice on Demux AW channel.
  localparam logic [9:0] DemuxAw = (1 << 9);
  /// Slice on Demux W channel.
  localparam logic [9:0] DemuxW  = (1 << 8);
  /// Slice on Demux B channel.
  localparam logic [9:0] DemuxB  = (1 << 7);
  /// Slice on Demux AR channel.
  localparam logic [9:0] DemuxAr = (1 << 6);
  /// Slice on Demux R channel.
  localparam logic [9:0] DemuxR  = (1 << 5);
  /// Slice on Mux AW channel.
  localparam logic [9:0] MuxAw   = (1 << 4);
  /// Slice on Mux W channel.
  localparam logic [9:0] MuxW    = (1 << 3);
  /// Slice on Mux B channel.
  localparam logic [9:0] MuxB    = (1 << 2);
  /// Slice on Mux AR channel.
  localparam logic [9:0] MuxAr   = (1 << 1);
  /// Slice on Mux R channel.
  localparam logic [9:0] MuxR    = (1 << 0);
  /// Latency configuration for `axi_xbar`.
  typedef enum logic [9:0] {
    NO_LATENCY    = 10'b000_00_000_00,
    CUT_SLV_AX    = DemuxAw | DemuxAr,
    CUT_MST_AX    = MuxAw | MuxAr,
    CUT_ALL_AX    = DemuxAw | DemuxAr | MuxAw | MuxAr,
    CUT_SLV_PORTS = DemuxAw | DemuxW | DemuxB | DemuxAr | DemuxR,
    CUT_MST_PORTS = MuxAw | MuxW | MuxB | MuxAr | MuxR,
    CUT_ALL_PORTS = 10'b111_11_111_11
  } xbar_latency_e;

  /// Configuration for `axi_xbar`.
  typedef struct packed {
    /// Number of slave ports of the crossbar.
    /// This many master modules are connected to it.
    int unsigned   NoSlvPorts;
    /// Number of master ports of the crossbar.
    /// This many slave modules are connected to it.
    int unsigned   NoMstPorts;
    /// Maximum number of open transactions each master connected to the crossbar can have in
    /// flight at the same time.
    int unsigned   MaxMstTrans;
    /// Maximum number of open transactions each slave connected to the crossbar can have in
    /// flight at the same time.
    int unsigned   MaxSlvTrans;
    /// Determine if the internal FIFOs of the crossbar are instantiated in fallthrough mode.
    /// 0: No fallthrough
    /// 1: Fallthrough
    bit            FallThrough;
    /// The Latency mode of the xbar. This determines if the channels on the ports have
    /// a spill register instantiated.
    /// Example configurations are provided with the enum `xbar_latency_e`.
    xbar_latency_e LatencyMode;
    /// This is the number of `axi_multicut` stages instantiated in the line cross of the channels.
    /// Having multiple stages can potentially add a large number of FFs!
    int unsigned   PipelineStages;
    /// AXI ID width of the salve ports. The ID width of the master ports is determined
    /// Automatically. See `axi_mux` for details.
    int unsigned   AxiIdWidthSlvPorts;
    /// The used ID portion to determine if a different salve is used for the same ID.
    /// See `axi_demux` for details.
    int unsigned   AxiIdUsedSlvPorts;
    /// Are IDs unique?
    bit            UniqueIds;
    /// AXI4+ATOP address field width.
    int unsigned   AxiAddrWidth;
    /// AXI4+ATOP data field width.
    int unsigned   AxiDataWidth;
    /// The number of address rules defined for routing of the transactions.
    /// Each master port can have multiple rules, should have however at least one.
    /// If a transaction can not be routed the xbar will answer with an `axi_pkg::RESP_DECERR`.
    int unsigned   NoAddrRules;
  } xbar_cfg_t;

  /// Commonly used rule types for `axi_xbar` (64-bit addresses).
  typedef struct packed {
    int unsigned idx;
    logic [63:0] start_addr;
    logic [63:0] end_addr;
  } xbar_rule_64_t;

  /// Commonly used rule types for `axi_xbar` (32-bit addresses).
  typedef struct packed {
    int unsigned idx;
    logic [31:0] start_addr;
    logic [31:0] end_addr;
  } xbar_rule_32_t;

endpackage