design/sys/iop/dmu/rtl/dmu_dsn_ccc_pkt.v

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// OpenSPARC T2 Processor File: dmu_dsn_ccc_pkt.v
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module dmu_dsn_ccc_pkt
  (
   clk,
   rst_l,

   wr_req_vld,
   cdp2pkt_addr,
   cdp2pkt_data,
//   cdp2pkt_src_bus,
   buf_id_in,

   fsm2pkt_valid,

   j2d_csr_ring_out,
   pkt2ctl_dbg_grp_b_1
   );

// ----------------------------------------------------------------------------
// Parameters
// ----------------------------------------------------------------------------
  parameter     IDLE = 2'b00,           // state machine states
                RDMS = 2'b01,
                RDLS = 2'b10,
                BUSY = 2'b11;

// ----------------------------------------------------------------------------
// Ports
// ----------------------------------------------------------------------------
  input                                 clk;
  input                                 rst_l;

  input  [`FIRE_CSR_DATA_BITS]          cdp2pkt_data;
//  input  [`FIRE_CSR_SRCB_BITS]                cdp2pkt_src_bus;
  input  [1:0]                          buf_id_in;
  input  [`FIRE_CSR_ADDR_BITS]          cdp2pkt_addr;

  input                                 wr_req_vld;
  input                                 fsm2pkt_valid;

  output [`FIRE_CSR_RING_BITS]          j2d_csr_ring_out;
  output [2:0]                          pkt2ctl_dbg_grp_b_1;

// ----------------------------------------------------------------------------
// Variables
// ----------------------------------------------------------------------------
  wire [`FIRE_CSR_RING_BITS]            j2d_csr_ring_out, addr_phase;
  wire [`FIRE_CSR_CMND_BITS]            cmnd;

  reg  [`FIRE_CSR_RING_BITS]            ring, nxt_ring;
  reg  [1:0]                            state, nxt_state;
  reg  [1:0]                            select;

// ----------------------------------------------------------------------------
// Zero In Checkers
// ----------------------------------------------------------------------------

// ----------------------------------------------------------------------------
// Combinational
// ----------------------------------------------------------------------------
  assign j2d_csr_ring_out = ring;

// next state
  always @ (state or fsm2pkt_valid) begin
        nxt_state       = IDLE;
    case (state)
      IDLE : begin
        if (fsm2pkt_valid) nxt_state = RDMS;
        else               nxt_state = IDLE;
      end
      RDMS :               nxt_state = RDLS;
      RDLS :               nxt_state = BUSY;
      BUSY : begin
        if (fsm2pkt_valid) nxt_state = BUSY;
        else               nxt_state = IDLE;
      end
//      default:        nxt_state = 2'bxx;
    endcase
  end

  always @ (state or fsm2pkt_valid or wr_req_vld) begin
        select = 2'b00;
    case (state)
      IDLE : begin
        if (fsm2pkt_valid) begin
          select  = 2'b01;
        end
        else begin
          select  = 2'b00;
        end
      end
      RDMS : begin
        select  = {wr_req_vld, 1'b0};
      end
      RDLS : begin
        select  = {wr_req_vld, wr_req_vld};
      end
      BUSY : begin
        select  = 2'b00;
      end
//      default:        select = 2'bxx;
    endcase
  end

  assign cmnd = wr_req_vld ? `FIRE_CSR_CMND_WREQ : `FIRE_CSR_CMND_RREQ;
//BP 3-08-04 src bus decodes for fast, medium and slow, see FIRE/JBC MAS sec. 6.15.11.3.4
wire    [1:0]   cdp2pkt_src_bus;
wire    fast_bus, medium_bus, slow_bus;
//BP 4.29.04 note these decodes are using addresses such that the bit positions are byte aligned
// see the code /jbc/csr/ars/ops/rtl/fire_jlc_csr_ars.v  line 333
assign fast_bus          = ( (cdp2pkt_addr[19:16] == 4'h0) ||           // fast bus
                                (cdp2pkt_addr[19:16] == 4'h1) ||
                                (cdp2pkt_addr[19:16] == 4'h2) ||
                                (cdp2pkt_addr[19:16] == 4'h3) );
assign medium_bus        = ( (cdp2pkt_addr[19:16] == 4'h4) ||           // medium bus
                                (cdp2pkt_addr[19:16] == 4'h5) ||
                                (cdp2pkt_addr[19:16] == 4'h6) ||
                                (cdp2pkt_addr[19:16] == 4'h7) );
assign slow_bus         = ( (cdp2pkt_addr[19:16] == 4'h8) ||            // slow bus
                                (cdp2pkt_addr[19:16] == 4'h9) ||
                                (cdp2pkt_addr[19:16] == 4'ha) ||
                                (cdp2pkt_addr[19:16] == 4'hb) ||
                                (cdp2pkt_addr[19:16] == 4'hc) ||
                                (cdp2pkt_addr[19:16] == 4'hd) ||
                                (cdp2pkt_addr[19:16] == 4'he) ||
                                (cdp2pkt_addr[19:16] == 4'hf) );
assign  cdp2pkt_src_bus[0] = (fast_bus || slow_bus) && ~buf_id_in[0];
assign  cdp2pkt_src_bus[1] = (fast_bus || medium_bus) && ~buf_id_in[0];
  assign addr_phase[`FIRE_CSR_RING_CMND_BITS] = cmnd;
  assign addr_phase[`FIRE_CSR_RING_SRCB_BITS] = cdp2pkt_src_bus;
// BP note: cdp2pkt_addr in N2 is a byte address, so I need to drop the bottom 3 bits here
//      because the address out onto the ring is [22:3]
  assign addr_phase[`FIRE_CSR_RING_ADDR_BITS] = {3'b0,cdp2pkt_addr[26:3]};

  always @ (select or addr_phase or cdp2pkt_data) begin
        nxt_ring        = 0;
    case (select) // synopsys infer_mux
      2'b00 : nxt_ring = 0;
      2'b01 : nxt_ring = addr_phase;
      2'b10 : nxt_ring = cdp2pkt_data[`FIRE_CSR_RDMS_BITS];
      2'b11 : nxt_ring = cdp2pkt_data[`FIRE_CSR_RDLS_BITS];
//      default         nxt_ring = 32'bxxxx_xxxx_xxxx_xxxx_xxxx_xxxx_xxxx_xxxx;
    endcase
  end

// ----------------------------------------------------------------------------
// Sequential
// ----------------------------------------------------------------------------
  always  @ (posedge clk) begin
    if (!rst_l) begin
      ring  <= 0;
      state <= IDLE;
    end
    else begin
      ring  <= nxt_ring;
      state <= nxt_state;
    end
  end

// ----------------------------------------------------------------------------
// debug --- for dbg group b sub sel 1
// ----------------------------------------------------------------------------
assign  pkt2ctl_dbg_grp_b_1[2:0] = cmnd[2:0];

endmodule // dmu_dsn_ddd_pkt