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

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// OpenSPARC T2 Processor File: dmu_dsn_ccc_fsm.v
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module dmu_dsn_ccc_fsm
  (
   clk,
   rst_l,
   rd_req_vld,
   wr_req_vld,
   dep2fsm_acc_vio,
   dep2fsm_done,
   dep2fsm_valid,
   ack_busy,
   rd_ack_vld,
   rd_nack_vld,
   fsm2arb_done,
   fsm2pkt_valid,
   fsm2ctl_dbg_grp_b_1
   );

// ----------------------------------------------------------------------------
// Parameters
// ----------------------------------------------------------------------------
  parameter     IDLE = 3'b000,          // state machine states
                RQST = 3'b001,
                WAIT = 3'b010,
//              MAPD = 3'b011,
                DONE = 3'b110,
                AVIO = 3'b100,
                MDTO = 3'b101,
                SKIP = 3'b111;

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


  input                                 rd_req_vld;
  input                                 wr_req_vld;


  input                                 dep2fsm_acc_vio;
  input                                 dep2fsm_done;
  input                                 dep2fsm_valid;
  input                                 ack_busy;


  output                                fsm2arb_done;
  output                                rd_ack_vld;
  output                                rd_nack_vld;
  output                                fsm2pkt_valid;
  output [4:0]                          fsm2ctl_dbg_grp_b_1;

// ----------------------------------------------------------------------------
// Variables
// ----------------------------------------------------------------------------
  reg                                   fsm2arb_done;
  reg                                   fsm2cdp_stts;
  reg                                   fsm2pkt_valid;

  reg [2:0]                             state, nxt_state;
  reg [`FIRE_CSR_TOUT_BITS]             timer, nxt_timer;

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

// csr_ring_fsm
    //0in state_transition  -var state  -val IDLE  -next IDLE MDTO RQST
    //0in state_transition  -var state  -val RQST  -next WAIT RQST
    //0in state_transition  -var state  -val WAIT  -next AVIO DONE MDTO WAIT
    //0in state_transition  -var state  -val DONE  -next SKIP
    //0in state_transition  -var state  -val MDTO  -next SKIP
    //0in state_transition  -var state  -val AVIO  -next SKIP
    //0in state_transition  -var state  -val SKIP  -next IDLE


// ----------------------------------------------------------------------------
// Combinational
// ----------------------------------------------------------------------------

// timeout
  wire   timeout = ~|timer;

// arb valid and map error
  wire   arb_vld = (rd_req_vld | wr_req_vld) && ~ack_busy;
  wire   map_err = 1'b0;

// access violation, request valid, and response valid
  wire   acc_vio = dep2fsm_valid &  dep2fsm_done &  dep2fsm_acc_vio;
//BP 3-17-04 req_vld should be 1 at the beginning of the csr ring transfer, right????
  wire   req_vld = dep2fsm_valid & ~dep2fsm_done & ~dep2fsm_acc_vio;
  wire   rsp_vld = dep2fsm_valid &   dep2fsm_done & ~dep2fsm_acc_vio;
//BP 5-07-04
 wire   rd_ack_vld = fsm2arb_done & ~fsm2cdp_stts & rd_req_vld;
 wire   rd_nack_vld = fsm2arb_done & fsm2cdp_stts & rd_req_vld;
// next state
  always @ (state or arb_vld or acc_vio or map_err or
            req_vld or rsp_vld or timeout) begin
        nxt_state       = IDLE;
    case (state) // synopsys parallel_case
      IDLE : begin
        if (!arb_vld)     nxt_state = IDLE;
        else if (map_err) nxt_state = MDTO;
        else              nxt_state = RQST;
      end
      RQST : begin
        if (req_vld)      nxt_state = WAIT;
        else              nxt_state = RQST;
      end
      WAIT : begin
        if (acc_vio)      nxt_state = AVIO;
        else if (rsp_vld) nxt_state = DONE;
        else if (timeout) nxt_state = MDTO;
        else              nxt_state = WAIT;
      end
      DONE :              nxt_state = SKIP;
      MDTO :              nxt_state = SKIP;
      AVIO :              nxt_state = SKIP;
      SKIP :              nxt_state = IDLE;
        default:        begin
                        nxt_state       = 3'b000;       //0in < fire  -message " got x's in dsn_ccc_fsm"
                        end
    endcase
  end

// state outputs
  always @ (state or timer ) begin
    fsm2arb_done  = 1'b0;
    fsm2cdp_stts  = 1'b0;
    fsm2pkt_valid = 1'b0;
    nxt_timer     = 8'b11100000;
    case (state) // synopsys parallel_case
      IDLE : begin
        end
      RQST : begin
        fsm2pkt_valid = 1'b1;
      end
      WAIT : begin
        fsm2pkt_valid = 1'b1;
        nxt_timer     = timer - 8'b00000001;
      end
      DONE : begin
        fsm2arb_done  = 1'b1;
      end
      MDTO : begin
        fsm2arb_done  = 1'b1;
        fsm2cdp_stts  = 1'b1;
      end
      AVIO : begin
        fsm2arb_done  = 1'b1;
        fsm2cdp_stts  = 1'b1;
      end
      SKIP : begin
        fsm2pkt_valid = 1'b0;
        fsm2arb_done  = 1'b0;
      end
        default:        begin
                        fsm2arb_done    = 1'b0;
                        fsm2pkt_valid   = 1'b0;
                        fsm2cdp_stts    = 1'b0;
                        nxt_timer       = 8'b00000000;
                        end
    endcase
  end

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

  always @ (posedge clk)
    if (!rst_l) begin
    timer <= 8'b0;
  end
    else begin
    timer <= nxt_timer;
  end

// ----------------------------------------------------------------------------
// debug--  debug signals for debug group b sub_sel 1
// ----------------------------------------------------------------------------
assign  fsm2ctl_dbg_grp_b_1[4:0] = {arb_vld,req_vld,acc_vio,rsp_vld,timeout};

endmodule // dmu_dsn_ccc_fsm