ddr2_model.v

DDR2 SDRAM仿真模型

                            row_pipeline[2*write_latency + 1] = active_row[bank];
                            col_pipeline[2*write_latency + 1] = col;
                            ck_bank_write[bank] <= ck_cntr;
                            ck_write <= ck_cntr;
                        end
                    end
                    READ : begin
                        if (!dll_locked)
                            $display ("%m: at time %t WARNING: %s prior to DLL locked.  Failing to wait for synchronization to occur may result in a violation of the tAC or tDQSCK parameters.", $time, cmd_string[cmd]);
                        if (!init_done) begin
                            $display ("%m: at time %t ERROR: %s Failure.  Initialization sequence is not complete.", $time, cmd_string[cmd]);
                            if (STOP_ON_ERROR) $stop(0);
                        end else if (!active_bank[bank]) begin
                            $display ("%m: at time %t ERROR: %s Failure.  Bank %d must be Activated.", $time, cmd_string[cmd], bank);
                            if (STOP_ON_ERROR) $stop(0);
                        end else if (auto_precharge_bank[bank]) begin
                            $display ("%m: at time %t ERROR: %s Failure.  Auto Precharge is scheduled to bank %d.", $time, cmd_string[cmd], bank);
                            if (STOP_ON_ERROR) $stop(0);
                        end else if ((ck_cntr - ck_read < burst_length/2) && (ck_cntr - ck_read)%2) begin
                            $display ("%m: at time %t ERROR: %s Failure.  Illegal burst interruption.", $time, cmd_string[cmd]);
                            if (STOP_ON_ERROR) $stop(0);
                        end else begin
                            if (addr[AP]) begin
                                auto_precharge_bank[bank] = 1'b1;
                                read_precharge_bank[bank] = 1'b1;
                            end
                            col = ((addr>>1) & -1*(1<<AP)) | (addr & {AP{1'b1}});
                            if (col >= 1<<COL_BITS) begin
                                $display ("%m: at time %t WARNING: col = %h does not exist.  Maximum col = %h", $time, col, (1<<COL_BITS)-1);
                            end
                            if (DEBUG) $display ("%m: at time %t INFO: %s bank %d col %h, auto precharge %d", $time, cmd_string[cmd], bank, col, addr[AP]);
                            rd_pipeline[2*read_latency - 1]  = 1;
                            ba_pipeline[2*read_latency - 1]  = bank;
                            row_pipeline[2*read_latency - 1] = active_row[bank];
                            col_pipeline[2*read_latency - 1] = col;
                            ck_bank_read[bank] <= ck_cntr;
                            ck_read <= ck_cntr;
                        end
                    end
                    NOP: begin
                        if (in_power_down) begin
                            if (DEBUG) $display ("%m: at time %t INFO: Power Down Exit", $time);
                            in_power_down = 0;
                            if (|active_bank & low_power) begin // slow exit active power down
                                ck_slow_exit_pd <= ck_cntr;
                            end
                            ck_power_down <= ck_cntr;
                        end
                        if (in_self_refresh) begin
                            if ($time - tm_cke < TISXR)
                                $display ("%m: at time %t ERROR: tISXR violation during Self Refresh Exit", $time);
                            if (DEBUG) $display ("%m: at time %t INFO: Self Refresh Exit", $time);
                            in_self_refresh = 0;
                            ck_dll_reset <= ck_cntr;
                            ck_self_refresh <= ck_cntr;
                            tm_self_refresh <= $time;
                            tm_refresh <= $time;
                        end
                    end
                endcase
                if ((prev_cke !== 1) && (cmd !== NOP)) begin
                    $display ("%m: at time %t ERROR: NOP or Deselect is required when CKE goes active.", $time);
                end
                if (!init_done) begin
                    case (init_step)
                        0 : begin
                            if ($time < 200000000) 
                                $display ("%m at time %t WARNING: 200 us is required before CKE goes active.", $time);
//                          if (cmd_chk + 200000000 > $time)
//                              $display("%m: at time %t WARNING: NOP or DESELECT is required for 200 us before CKE is brought high", $time);
                            init_step = init_step + 1;
                        end
                        1 : if (dll_en)        init_step = init_step + 1;
                        2 : begin
                            if (&init_mode_reg && dll_reset) begin
                                active_bank = {`BANKS{1'b1}};   // require Precharge All or bank Precharges
                                ref_cntr = 0;                   // require refresh
                                init_step = init_step + 1;
                            end
                        end
                        3 : if (ref_cntr == 2) begin
                            init_step = init_step + 1;
                        end
                        4 : if (!dll_reset)    init_step = init_step + 1;
                        5 : if (ocd == 3'b111) init_step = init_step + 1;
                        6 : begin
                            if (ocd == 3'b000) begin
                                if (DEBUG) $display ("%m: at time %t INFO: Initialization Sequence is complete", $time);
                                init_done = 1;
                            end
                        end
                    endcase
                end
            end else if (prev_cke) begin
                if ((!init_done) && (init_step > 1)) begin
                    $display ("%m: at time %t ERROR: CKE must remain active until the initialization sequence is complete.", $time);
                    if (STOP_ON_ERROR) $stop(0);
                end
                case (cmd)
                    REFRESH : begin
                        for (j=0; j<NOP; j=j+1) begin
                            chk_err(1'b0, bank, j, SELF_REF);
                        end
                        chk_err(1'b0, bank, PWR_DOWN, SELF_REF);
                        chk_err(1'b0, bank, SELF_REF, SELF_REF);
                        if (|active_bank) begin
                            $display ("%m: at time %t ERROR: Self Refresh Failure.  All banks must be Precharged.", $time);
                            if (STOP_ON_ERROR) $stop(0);
                            init_done = 0;
                        end else if (odt_en && odt_state) begin
                            $display ("%m: at time %t ERROR: ODT must be off prior to entering Self Refresh", $time);
                            if (STOP_ON_ERROR) $stop(0);
                            init_done = 0;
                        end else if (!init_done) begin
                            $display ("%m: at time %t ERROR: Self Refresh Failure.  Initialization sequence is not complete.", $time);
                            if (STOP_ON_ERROR) $stop(0);
                        end else begin
                            if (DEBUG) $display ("%m: at time %t INFO: Self Refresh Enter", $time);
                            in_self_refresh = 1;
                            dll_locked = 0;
                        end
                    end
                    NOP : begin
                        // entering slow_exit or precharge power down and tANPD has not been satisfied
                        if ((low_power || (active_bank == 0)) && (ck_cntr - ck_odt < TANPD))
                            $display ("%m: at time %t WARNING: tANPD violation during %s.  Synchronous or asynchronous change in termination resistance is possible.", $time, cmd_string[PWR_DOWN]);
                        for (j=0; j<NOP; j=j+1) begin
                            chk_err(1'b0, bank, j, PWR_DOWN);
                        end
                        chk_err(1'b0, bank, PWR_DOWN, PWR_DOWN);
                        chk_err(1'b0, bank, SELF_REF, PWR_DOWN);

                        if (!init_done) begin
                            $display ("%m: at time %t ERROR: Power Down Failure.  Initialization sequence is not complete.", $time);
                            if (STOP_ON_ERROR) $stop(0);
                        end else begin
                            if (DEBUG) begin
                                if (|active_bank) begin
                                    $display ("%m: at time %t INFO: Active Power Down Enter", $time);
                                end else begin
                                    $display ("%m: at time %t INFO: Precharge Power Down Enter", $time);
                                end
                            end
                            in_power_down = 1;
                        end
                    end
                    default : begin
                        $display ("%m: at time %t ERROR: NOP, Deselect, or Refresh is required when CKE goes inactive.", $time);
                        init_done = 0;
                    end
                endcase
                if (!init_done) begin
                    if (DEBUG) $display ("%m: at time %t INFO: Reset has occurred.", $time);
                    reset_task;
                end
            end
            prev_cke  = cke;
        end
    endtask

    task data_task;
        reg [BA_BITS-1:0] bank;
        reg [ROW_BITS-1:0] row;
        reg [COL_BITS-1:0] col;
        integer i;
        integer j;
        begin

            if (diff_ck) begin
                for (i=0; i<32; i=i+1) begin
                    if (dq_in_valid && dll_locked && ($time - tm_dqs_neg[i] < $rtoi(TDSS*tck_avg)))
                        $display ("%m: at time %t ERROR: tDSS violation on %s bit %d", $time, dqs_string[i/16], i%16);
                    if (check_write_dqs_high[i])
                        $display ("%m: at time %t ERROR: %s bit %d latching edge required during the preceding clock period.", $time, dqs_string[i/16], i%16);
                end
                check_write_dqs_high <= 0;
            end else begin
                for (i=0; i<32; i=i+1) begin
                    if (dll_locked && dq_in_valid) begin
                        tm_tdqss = abs_value($itor(tm_ck_pos) - tm_dqss_pos[i]);
                        if ((tm_tdqss < tck_avg/2.0) && (tm_tdqss > TDQSS*tck_avg))
                            $display ("%m: at time %t ERROR: tDQSS violation on %s bit %d", $time, dqs_string[i/16], i%16); 
                    end
                    if (check_write_dqs_low[i])
                        $display ("%m: at time %t ERROR: %s bit %d latching edge required during the preceding clock period", $time, dqs_string[i/16], i%16);
                end
                check_write_preamble <= 0;
                check_write_postamble <= 0;
                check_write_dqs_low <= 0;
            end

            if (wr_pipeline[0] || rd_pipeline[0]) begin
                bank = ba_pipeline[0];
                row = row_pipeline[0];
                col = col_pipeline[0];
                burst_cntr = 0;
                memory_read(bank, row, col, memory_data);
            end

            // burst counter
            if (burst_cntr < burst_length) begin
                burst_position = col ^ burst_cntr;
                if (!burst_order) begin
                    burst_position[BO_BITS-1:0] = col + burst_cntr;
                end
                burst_cntr = burst_cntr + 1;
            end

            // write dqs counter
            if (wr_pipeline[WDQS_PRE + 1]) begin
                wdqs_cntr = WDQS_PRE + burst_length + WDQS_PST - 1;
            end
            // write dqs
            if ((wdqs_cntr == burst_length + WDQS_PST) && (wdq_cntr == 0)) begin //write preamble
                check_write_preamble <= ({DQS_BITS{dqs_n_en}}<<16) | {DQS_BITS{1'b1}};
            end
            if (wdqs_cntr > 1) begin  // write data
                if ((wdqs_cntr - WDQS_PST)%2) begin
                    check_write_dqs_high <= ({DQS_BITS{dqs_n_en}}<<16) | {DQS_BITS{1'b1}};
                end else begin
                    check_write_dqs_low <= ({DQS_BITS{dqs_n_en}}<<16) | {DQS_BITS{1'b1}};
                end
            end
            if (wdqs_cntr == WDQS_PST) begin // write postamble
                check_write_postamble <= ({DQS_BITS{dqs_n_en}}<<16) | {DQS_BITS{1'b1}};
            end 
            if (wdqs_cntr > 0) begin
                wdqs_cntr = wdqs_cntr - 1;
            end

            // write dq