IPCores/lm32_cpu: lm32_load_store_unit.v@cd0b58aa6f83 (annotated)

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lm32_load_store_unit.v@cd0b58aa6f83 (annotated)

lm32_load_store_unit.v

Sun, 04 Apr 2010 20:40:03 +0100

author: Philip Pemberton <philpem@philpem.me.uk>
date: Sun, 04 Apr 2010 20:40:03 +0100
changeset 0: cd0b58aa6f83
child 8: 07be9df9fee8
permissions: -rw-r--r--

add lm32 source

 // =============================================================================
 //                           COPYRIGHT NOTICE
 // Copyright 2006 (c) Lattice Semiconductor Corporation
 // ALL RIGHTS RESERVED
 // This confidential and proprietary software may be used only as authorised by
 // a licensing agreement from Lattice Semiconductor Corporation.
 // The entire notice above must be reproduced on all authorized copies and
 // copies may only be made to the extent permitted by a licensing agreement from
 // Lattice Semiconductor Corporation.
 //
 // Lattice Semiconductor Corporation        TEL : 1-800-Lattice (USA and Canada)
 // 5555 NE Moore Court                            408-826-6000 (other locations)
 // Hillsboro, OR 97124                     web  : http://www.latticesemi.com/
 // U.S.A                                   email: techsupport@latticesemi.com
 // =============================================================================/
 //                         FILE DETAILS
 // Project      : LatticeMico32
 // File         : lm32_load_store_unit.v
 // Title        : Load and store unit
 // Dependencies : lm32_include.v
 // Version      : 6.1.17
 //              : Initial Release
 // Version      : 7.0SP2, 3.0
 //              : No Change
 // Version      : 3.1
 //              : Instead of disallowing an instruction cache miss on a data cache
 //              : miss, both can now occur at the same time. If both occur at same
 //              : time, then restart address is the address of instruction that
 //              : caused data cache miss.
 // Version      : 3.2
 //              : EBRs use SYNC resets instead of ASYNC resets.
 // Version      : 3.3
 //              : Support for new non-cacheable Data Memory that is accessible by
 //              : the data port and has a one cycle access latency.
 // Version      : 3.4
 //              : No change
 // Version      : 3.5
 //              : Bug fix: Inline memory is correctly generated if it is not a
 //              : power-of-two
 // =============================================================================
 `include "lm32_include.v"
 /////////////////////////////////////////////////////
 // Module interface
 /////////////////////////////////////////////////////
 module lm32_load_store_unit (
     // ----- Inputs -------
     clk_i,
     rst_i,
     // From pipeline
     stall_a,
     stall_x,
     stall_m,
     kill_x,
     kill_m,
     exception_m,
     store_operand_x,
     load_store_address_x,
     load_store_address_m,
     load_store_address_w,
     load_x,
     store_x,
     load_q_x,
     store_q_x,
     load_q_m,
     store_q_m,
     sign_extend_x,
     size_x,
 `ifdef CFG_DCACHE_ENABLED
     dflush,
 `endif
 `ifdef CFG_IROM_ENABLED
     irom_data_m,
 `endif
     // From Wishbone
     d_dat_i,
     d_ack_i,
     d_err_i,
     d_rty_i,
     // ----- Outputs -------
     // To pipeline
 `ifdef CFG_DCACHE_ENABLED
     dcache_refill_request,
     dcache_restart_request,
     dcache_stall_request,
     dcache_refilling,
 `endif
 `ifdef CFG_IROM_ENABLED
     irom_store_data_m,
     irom_address_xm,
     irom_we_xm,
     irom_stall_request_x,
 `endif
     load_data_w,
     stall_wb_load,
     // To Wishbone
     d_dat_o,
     d_adr_o,
     d_cyc_o,
     d_sel_o,
     d_stb_o,
     d_we_o,
     d_cti_o,
     d_lock_o,
     d_bte_o
     );
 /////////////////////////////////////////////////////
 // Parameters
 /////////////////////////////////////////////////////
 parameter associativity = 1;                            // Associativity of the cache (Number of ways)
 parameter sets = 512;                                   // Number of sets
 parameter bytes_per_line = 16;                          // Number of bytes per cache line
 parameter base_address = 0;                             // Base address of cachable memory
 parameter limit = 0;                                    // Limit (highest address) of cachable memory
 // For bytes_per_line == 4, we set 1 so part-select range isn't reversed, even though not really used
 localparam addr_offset_width = bytes_per_line == 4 ? 1 : clogb2(bytes_per_line)-1-2;
 localparam addr_offset_lsb = 2;
 localparam addr_offset_msb = (addr_offset_lsb+addr_offset_width-1);
 /////////////////////////////////////////////////////
 // Inputs
 /////////////////////////////////////////////////////
 input clk_i;                                            // Clock
 input rst_i;                                            // Reset
 input stall_a;                                          // A stage stall
 input stall_x;                                          // X stage stall
 input stall_m;                                          // M stage stall
 input kill_x;                                           // Kill instruction in X stage
 input kill_m;                                           // Kill instruction in M stage
 input exception_m;                                      // An exception occured in the M stage
 input [`LM32_WORD_RNG] store_operand_x;                 // Data read from register to store
 input [`LM32_WORD_RNG] load_store_address_x;            // X stage load/store address
 input [`LM32_WORD_RNG] load_store_address_m;            // M stage load/store address
 input [1:0] load_store_address_w;                       // W stage load/store address (only least two significant bits are needed)
 input load_x;                                           // Load instruction in X stage
 input store_x;                                          // Store instruction in X stage
 input load_q_x;                                         // Load instruction in X stage
 input store_q_x;                                        // Store instruction in X stage
 input load_q_m;                                         // Load instruction in M stage
 input store_q_m;                                        // Store instruction in M stage
 input sign_extend_x;                                    // Whether load instruction in X stage should sign extend or zero extend
 input [`LM32_SIZE_RNG] size_x;                          // Size of load or store (byte, hword, word)
 `ifdef CFG_DCACHE_ENABLED
 input dflush;                                           // Flush the data cache
 `endif
 `ifdef CFG_IROM_ENABLED
 input [`LM32_WORD_RNG] irom_data_m;                     // Data from Instruction-ROM
 `endif
 input [`LM32_WORD_RNG] d_dat_i;                         // Data Wishbone interface read data
 input d_ack_i;                                          // Data Wishbone interface acknowledgement
 input d_err_i;                                          // Data Wishbone interface error
 input d_rty_i;                                          // Data Wishbone interface retry
 /////////////////////////////////////////////////////
 // Outputs
 /////////////////////////////////////////////////////
 `ifdef CFG_DCACHE_ENABLED
 output dcache_refill_request;                           // Request to refill data cache
 wire   dcache_refill_request;
 output dcache_restart_request;                          // Request to restart the instruction that caused a data cache miss
 wire   dcache_restart_request;
 output dcache_stall_request;                            // Data cache stall request
 wire   dcache_stall_request;
 output dcache_refilling;
 wire   dcache_refilling;
 `endif
 `ifdef CFG_IROM_ENABLED
 output irom_store_data_m;                               // Store data to Instruction ROM
 wire   [`LM32_WORD_RNG] irom_store_data_m;
 output [`LM32_WORD_RNG] irom_address_xm;                // Load/store address to Instruction ROM
 wire   [`LM32_WORD_RNG] irom_address_xm;
 output irom_we_xm;                                      // Write-enable of 2nd port of Instruction ROM
 wire   irom_we_xm;
 output irom_stall_request_x;                            // Stall instruction in D stage
 wire   irom_stall_request_x;
 `endif
 output [`LM32_WORD_RNG] load_data_w;                    // Result of a load instruction
 reg    [`LM32_WORD_RNG] load_data_w;
 output stall_wb_load;                                   // Request to stall pipeline due to a load from the Wishbone interface
 reg    stall_wb_load;
 output [`LM32_WORD_RNG] d_dat_o;                        // Data Wishbone interface write data
 reg    [`LM32_WORD_RNG] d_dat_o;
 output [`LM32_WORD_RNG] d_adr_o;                        // Data Wishbone interface address
 reg    [`LM32_WORD_RNG] d_adr_o;
 output d_cyc_o;                                         // Data Wishbone interface cycle
 reg    d_cyc_o;
 output [`LM32_BYTE_SELECT_RNG] d_sel_o;                 // Data Wishbone interface byte select
 reg    [`LM32_BYTE_SELECT_RNG] d_sel_o;
 output d_stb_o;                                         // Data Wishbone interface strobe
 reg    d_stb_o;
 output d_we_o;                                          // Data Wishbone interface write enable
 reg    d_we_o;
 output [`LM32_CTYPE_RNG] d_cti_o;                       // Data Wishbone interface cycle type
 reg    [`LM32_CTYPE_RNG] d_cti_o;
 output d_lock_o;                                        // Date Wishbone interface lock bus
 reg    d_lock_o;
 output [`LM32_BTYPE_RNG] d_bte_o;                       // Data Wishbone interface burst type
 wire   [`LM32_BTYPE_RNG] d_bte_o;
 /////////////////////////////////////////////////////
 // Internal nets and registers
 /////////////////////////////////////////////////////
 // Microcode pipeline registers - See inputs for description
 reg [`LM32_SIZE_RNG] size_m;
 reg [`LM32_SIZE_RNG] size_w;
 reg sign_extend_m;
 reg sign_extend_w;
 reg [`LM32_WORD_RNG] store_data_x;
 reg [`LM32_WORD_RNG] store_data_m;
 reg [`LM32_BYTE_SELECT_RNG] byte_enable_x;
 reg [`LM32_BYTE_SELECT_RNG] byte_enable_m;
 wire [`LM32_WORD_RNG] data_m;
 reg [`LM32_WORD_RNG] data_w;
 `ifdef CFG_DCACHE_ENABLED
 wire dcache_select_x;                                   // Select data cache to load from / store to
 reg dcache_select_m;
 wire [`LM32_WORD_RNG] dcache_data_m;                    // Data read from cache
 wire [`LM32_WORD_RNG] dcache_refill_address;            // Address to refill data cache from
 reg dcache_refill_ready;                                // Indicates the next word of refill data is ready
 wire [`LM32_CTYPE_RNG] first_cycle_type;                // First Wishbone cycle type
 wire [`LM32_CTYPE_RNG] next_cycle_type;                 // Next Wishbone cycle type
 wire last_word;                                         // Indicates if this is the last word in the cache line
 wire [`LM32_WORD_RNG] first_address;                    // First cache refill address
 `endif
 `ifdef CFG_DRAM_ENABLED
 wire dram_select_x;                                     // Select data RAM to load from / store to
 reg dram_select_m;
 reg dram_bypass_en;                                     // RAW in data RAM; read latched (bypass) value rather than value from memory
 reg [`LM32_WORD_RNG] dram_bypass_data;                  // Latched value of store'd data to data RAM
 wire [`LM32_WORD_RNG] dram_data_out;                    // Data read from data RAM
 wire [`LM32_WORD_RNG] dram_data_m;                      // Data read from data RAM: bypass value or value from memory
 wire [`LM32_WORD_RNG] dram_store_data_m;                // Data to write to RAM
 `endif
 wire wb_select_x;                                       // Select Wishbone to load from / store to
 `ifdef CFG_IROM_ENABLED
 wire irom_select_x;                                     // Select instruction ROM to load from / store to
 reg  irom_select_m;
 `endif
 reg wb_select_m;
 reg [`LM32_WORD_RNG] wb_data_m;                         // Data read from Wishbone
 reg wb_load_complete;                                   // Indicates when a Wishbone load is complete
 /////////////////////////////////////////////////////
 // Functions
 /////////////////////////////////////////////////////
 `include "lm32_functions.v"
 /////////////////////////////////////////////////////
 // Instantiations
 /////////////////////////////////////////////////////
 `ifdef CFG_DRAM_ENABLED
    // Data RAM
    pmi_ram_dp_true
      #(
        // ----- Parameters -------
        .pmi_family             (`LATTICE_FAMILY),
        //.pmi_addr_depth_a       (1 << (clogb2(`CFG_DRAM_LIMIT/4-`CFG_DRAM_BASE_ADDRESS/4+1)-1)),
        //.pmi_addr_width_a       ((clogb2(`CFG_DRAM_LIMIT/4-`CFG_DRAM_BASE_ADDRESS/4+1)-1)),
        //.pmi_data_width_a       (`LM32_WORD_WIDTH),
        //.pmi_addr_depth_b       (1 << (clogb2(`CFG_DRAM_LIMIT/4-`CFG_DRAM_BASE_ADDRESS/4+1)-1)),
        //.pmi_addr_width_b       ((clogb2(`CFG_DRAM_LIMIT/4-`CFG_DRAM_BASE_ADDRESS/4+1)-1)),
        //.pmi_data_width_b       (`LM32_WORD_WIDTH),
        .pmi_addr_depth_a       (`CFG_DRAM_LIMIT/4-`CFG_DRAM_BASE_ADDRESS/4+1),
        .pmi_addr_width_a       (clogb2_v1(`CFG_DRAM_LIMIT/4-`CFG_DRAM_BASE_ADDRESS/4+1)),
        .pmi_data_width_a       (`LM32_WORD_WIDTH),
        .pmi_addr_depth_b       (`CFG_DRAM_LIMIT/4-`CFG_DRAM_BASE_ADDRESS/4+1),
        .pmi_addr_width_b       (clogb2_v1(`CFG_DRAM_LIMIT/4-`CFG_DRAM_BASE_ADDRESS/4+1)),
        .pmi_data_width_b       (`LM32_WORD_WIDTH),
        .pmi_regmode_a          ("noreg"),
        .pmi_regmode_b          ("noreg"),
        .pmi_gsr                ("enable"),
        .pmi_resetmode          ("sync"),
        .pmi_init_file          (`CFG_DRAM_INIT_FILE),
        .pmi_init_file_format   (`CFG_DRAM_INIT_FILE_FORMAT),
        .module_type            ("pmi_ram_dp_true")
        )
        ram (
 	    // ----- Inputs -------
 	    .ClockA                 (clk_i),
 	    .ClockB                 (clk_i),
 	    .ResetA                 (rst_i),
 	    .ResetB                 (rst_i),
 	    .DataInA                ({32{1'b0}}),
 	    .DataInB                (dram_store_data_m),
 	    .AddressA               (load_store_address_x[(clogb2(`CFG_DRAM_LIMIT/4-`CFG_DRAM_BASE_ADDRESS/4+1)-1)+2-1:2]),
 	    .AddressB               (load_store_address_m[(clogb2(`CFG_DRAM_LIMIT/4-`CFG_DRAM_BASE_ADDRESS/4+1)-1)+2-1:2]),
 	    // .ClockEnA               (!stall_x & (load_x | store_x)),
 	    .ClockEnA               (!stall_x),
 	    .ClockEnB               (!stall_m),
 	    .WrA                    (`FALSE),
 	    .WrB                    (store_q_m & dram_select_m),
 	    // ----- Outputs -------
 	    .QA                     (dram_data_out),
 	    .QB                     ()
 	    );
    /*----------------------------------------------------------------------
     EBRs cannot perform reads from location 'written to' on the same clock
     edge. Therefore bypass logic is required to latch the store'd value
     and use it for the load (instead of value from memory).
     ----------------------------------------------------------------------*/
    always @(posedge clk_i `CFG_RESET_SENSITIVITY)
      if (rst_i == `TRUE)
        begin
 	  dram_bypass_en <= `FALSE;
 	  dram_bypass_data <= 0;
        end
      else
        begin
 	  if (stall_x == `FALSE)
 	    dram_bypass_data <= dram_store_data_m;
 	  if (   (stall_m == `FALSE)
               && (stall_x == `FALSE)
 	      && (store_q_m == `TRUE)
 	      && (   (load_x == `TRUE)
 	          || (store_x == `TRUE)
 		 )
 	      && (load_store_address_x[(`LM32_WORD_WIDTH-1):2] == load_store_address_m[(`LM32_WORD_WIDTH-1):2])
 	     )
 	    dram_bypass_en <= `TRUE;
 	  else
 	    if (   (dram_bypass_en == `TRUE)
 		&& (stall_x == `FALSE)
 	       )
 	      dram_bypass_en <= `FALSE;
        end
    assign dram_data_m = dram_bypass_en ? dram_bypass_data : dram_data_out;
 `endif
 `ifdef CFG_DCACHE_ENABLED
 // Data cache
 lm32_dcache #(
     .associativity          (associativity),
     .sets                   (sets),
     .bytes_per_line         (bytes_per_line),
     .base_address           (base_address),
     .limit                  (limit)
     ) dcache (
     // ----- Inputs -----
     .clk_i                  (clk_i),
     .rst_i                  (rst_i),
     .stall_a                (stall_a),
     .stall_x                (stall_x),
     .stall_m                (stall_m),
     .address_x              (load_store_address_x),
     .address_m              (load_store_address_m),
     .load_q_m               (load_q_m & dcache_select_m),
     .store_q_m              (store_q_m & dcache_select_m),
     .store_data             (store_data_m),
     .store_byte_select      (byte_enable_m & {4{dcache_select_m}}),
     .refill_ready           (dcache_refill_ready),
     .refill_data            (wb_data_m),
     .dflush                 (dflush),
     // ----- Outputs -----
     .stall_request          (dcache_stall_request),
     .restart_request        (dcache_restart_request),
     .refill_request         (dcache_refill_request),
     .refill_address         (dcache_refill_address),
     .refilling              (dcache_refilling),
     .load_data              (dcache_data_m)
     );
 `endif
 /////////////////////////////////////////////////////
 // Combinational Logic
 /////////////////////////////////////////////////////
 // Select where data should be loaded from / stored to
 `ifdef CFG_DRAM_ENABLED
    assign dram_select_x =    (load_store_address_x >= `CFG_DRAM_BASE_ADDRESS)
                           && (load_store_address_x <= `CFG_DRAM_LIMIT);
 `endif
 `ifdef CFG_IROM_ENABLED
    assign irom_select_x =    (load_store_address_x >= `CFG_IROM_BASE_ADDRESS)
                           && (load_store_address_x <= `CFG_IROM_LIMIT);
 `endif
 `ifdef CFG_DCACHE_ENABLED
    assign dcache_select_x =    (load_store_address_x >= `CFG_DCACHE_BASE_ADDRESS)
                             && (load_store_address_x <= `CFG_DCACHE_LIMIT)
 `ifdef CFG_DRAM_ENABLED
                             && (dram_select_x == `FALSE)
 `endif
 `ifdef CFG_IROM_ENABLED
                             && (irom_select_x == `FALSE)
 `endif
                      ;
 `endif
    assign wb_select_x =    `TRUE
 `ifdef CFG_DCACHE_ENABLED
                         && !dcache_select_x
 `endif
 `ifdef CFG_DRAM_ENABLED
                         && !dram_select_x
 `endif
 `ifdef CFG_IROM_ENABLED
                         && !irom_select_x
 `endif
                      ;
 // Make sure data to store is in correct byte lane
 always @(*)
 begin
     case (size_x)
     `LM32_SIZE_BYTE:  store_data_x = {4{store_operand_x[7:0]}};
     `LM32_SIZE_HWORD: store_data_x = {2{store_operand_x[15:0]}};
     `LM32_SIZE_WORD:  store_data_x = store_operand_x;
     default:          store_data_x = {`LM32_WORD_WIDTH{1'bx}};
     endcase
 end
 // Generate byte enable accoring to size of load or store and address being accessed
 always @(*)
 begin
     casez ({size_x, load_store_address_x[1:0]})
     {`LM32_SIZE_BYTE, 2'b11}:  byte_enable_x = 4'b0001;
     {`LM32_SIZE_BYTE, 2'b10}:  byte_enable_x = 4'b0010;
     {`LM32_SIZE_BYTE, 2'b01}:  byte_enable_x = 4'b0100;
     {`LM32_SIZE_BYTE, 2'b00}:  byte_enable_x = 4'b1000;
     {`LM32_SIZE_HWORD, 2'b1?}: byte_enable_x = 4'b0011;
     {`LM32_SIZE_HWORD, 2'b0?}: byte_enable_x = 4'b1100;
     {`LM32_SIZE_WORD, 2'b??}:  byte_enable_x = 4'b1111;
     default:                   byte_enable_x = 4'bxxxx;
     endcase
 end
 `ifdef CFG_DRAM_ENABLED
 // Only replace selected bytes
 assign dram_store_data_m[`LM32_BYTE_0_RNG] = byte_enable_m[0] ? store_data_m[`LM32_BYTE_0_RNG] : dram_data_m[`LM32_BYTE_0_RNG];
 assign dram_store_data_m[`LM32_BYTE_1_RNG] = byte_enable_m[1] ? store_data_m[`LM32_BYTE_1_RNG] : dram_data_m[`LM32_BYTE_1_RNG];
 assign dram_store_data_m[`LM32_BYTE_2_RNG] = byte_enable_m[2] ? store_data_m[`LM32_BYTE_2_RNG] : dram_data_m[`LM32_BYTE_2_RNG];
 assign dram_store_data_m[`LM32_BYTE_3_RNG] = byte_enable_m[3] ? store_data_m[`LM32_BYTE_3_RNG] : dram_data_m[`LM32_BYTE_3_RNG];
 `endif
 `ifdef CFG_IROM_ENABLED
 // Only replace selected bytes
 assign irom_store_data_m[`LM32_BYTE_0_RNG] = byte_enable_m[0] ? store_data_m[`LM32_BYTE_0_RNG] : irom_data_m[`LM32_BYTE_0_RNG];
 assign irom_store_data_m[`LM32_BYTE_1_RNG] = byte_enable_m[1] ? store_data_m[`LM32_BYTE_1_RNG] : irom_data_m[`LM32_BYTE_1_RNG];
 assign irom_store_data_m[`LM32_BYTE_2_RNG] = byte_enable_m[2] ? store_data_m[`LM32_BYTE_2_RNG] : irom_data_m[`LM32_BYTE_2_RNG];
 assign irom_store_data_m[`LM32_BYTE_3_RNG] = byte_enable_m[3] ? store_data_m[`LM32_BYTE_3_RNG] : irom_data_m[`LM32_BYTE_3_RNG];
 `endif
 `ifdef CFG_IROM_ENABLED
    // Instead of implementing a byte-addressable instruction ROM (for store byte instruction),
    // a load-and-store architecture is used wherein a 32-bit value is loaded, the requisite
    // byte is replaced, and the whole 32-bit value is written back
    assign irom_address_xm = ((irom_select_m == `TRUE) && (store_q_m == `TRUE))
 	                    ? load_store_address_m
 	                    : load_store_address_x;
    // All store instructions perform a write operation in the M stage
    assign irom_we_xm =    (irom_select_m == `TRUE)
 	               && (store_q_m == `TRUE);
    // A single port in instruction ROM is available to load-store unit for doing loads/stores.
    // Since every store requires a load (in X stage) and then a store (in M stage), we cannot
    // allow load (or store) instructions sequentially after the store instructions to proceed
    // until the store instruction has vacated M stage (i.e., completed the store operation)
    assign irom_stall_request_x =    (irom_select_x == `TRUE)
 	                         && (store_q_x == `TRUE);
 `endif
 `ifdef CFG_DCACHE_ENABLED
  `ifdef CFG_DRAM_ENABLED
   `ifdef CFG_IROM_ENABLED
    // WB + DC + DRAM + IROM
    assign data_m = wb_select_m == `TRUE
                    ? wb_data_m
                    : dram_select_m == `TRUE
                      ? dram_data_m
                      : irom_select_m == `TRUE
                        ? irom_data_m
                        : dcache_data_m;
   `else
    // WB + DC + DRAM
    assign data_m = wb_select_m == `TRUE
                    ? wb_data_m
                    : dram_select_m == `TRUE
                      ? dram_data_m
                      : dcache_data_m;
   `endif
  `else
   `ifdef CFG_IROM_ENABLED
    // WB + DC + IROM
    assign data_m = wb_select_m == `TRUE
                    ? wb_data_m
                    : irom_select_m == `TRUE
                      ? irom_data_m
                      : dcache_data_m;
   `else
    // WB + DC
    assign data_m = wb_select_m == `TRUE
                    ? wb_data_m
                    : dcache_data_m;
   `endif
  `endif
 `else
  `ifdef CFG_DRAM_ENABLED
   `ifdef CFG_IROM_ENABLED
    // WB + DRAM + IROM
    assign data_m = wb_select_m == `TRUE
                    ? wb_data_m
                    : dram_select_m == `TRUE
                      ? dram_data_m
                      : irom_data_m;
   `else
    // WB + DRAM
    assign data_m = wb_select_m == `TRUE
                    ? wb_data_m
                    : dram_data_m;
   `endif
  `else
   `ifdef CFG_IROM_ENABLED
    // WB + IROM
    assign data_m = wb_select_m == `TRUE
                    ? wb_data_m
                    : irom_data_m;
   `else
    // WB
    assign data_m = wb_data_m;
   `endif
  `endif
 `endif
 // Sub-word selection and sign/zero-extension for loads
 always @(*)
 begin
     casez ({size_w, load_store_address_w[1:0]})
     {`LM32_SIZE_BYTE, 2'b11}:  load_data_w = {{24{sign_extend_w & data_w[7]}}, data_w[7:0]};
     {`LM32_SIZE_BYTE, 2'b10}:  load_data_w = {{24{sign_extend_w & data_w[15]}}, data_w[15:8]};
     {`LM32_SIZE_BYTE, 2'b01}:  load_data_w = {{24{sign_extend_w & data_w[23]}}, data_w[23:16]};
     {`LM32_SIZE_BYTE, 2'b00}:  load_data_w = {{24{sign_extend_w & data_w[31]}}, data_w[31:24]};
     {`LM32_SIZE_HWORD, 2'b1?}: load_data_w = {{16{sign_extend_w & data_w[15]}}, data_w[15:0]};
     {`LM32_SIZE_HWORD, 2'b0?}: load_data_w = {{16{sign_extend_w & data_w[31]}}, data_w[31:16]};
     {`LM32_SIZE_WORD, 2'b??}:  load_data_w = data_w;
     default:                   load_data_w = {`LM32_WORD_WIDTH{1'bx}};
     endcase
 end
 // Unused/constant Wishbone signals
 assign d_bte_o = `LM32_BTYPE_LINEAR;
 `ifdef CFG_DCACHE_ENABLED
 // Generate signal to indicate last word in cache line
 generate
     case (bytes_per_line)
 :
     begin
 assign first_cycle_type = `LM32_CTYPE_END;
 assign next_cycle_type = `LM32_CTYPE_END;
 assign last_word = `TRUE;
 assign first_address = {dcache_refill_address[`LM32_WORD_WIDTH-1:2], 2'b00};
     end
 :
     begin
 assign first_cycle_type = `LM32_CTYPE_INCREMENTING;
 assign next_cycle_type = `LM32_CTYPE_END;
 assign last_word = (&d_adr_o[addr_offset_msb:addr_offset_lsb]) == 1'b1;
 assign first_address = {dcache_refill_address[`LM32_WORD_WIDTH-1:addr_offset_msb+1], {addr_offset_width{1'b0}}, 2'b00};
     end
 :
     begin
 assign first_cycle_type = `LM32_CTYPE_INCREMENTING;
 assign next_cycle_type = d_adr_o[addr_offset_msb] == 1'b1 ? `LM32_CTYPE_END : `LM32_CTYPE_INCREMENTING;
 assign last_word = (&d_adr_o[addr_offset_msb:addr_offset_lsb]) == 1'b1;
 assign first_address = {dcache_refill_address[`LM32_WORD_WIDTH-1:addr_offset_msb+1], {addr_offset_width{1'b0}}, 2'b00};
     end
     endcase
 endgenerate
 `endif
 /////////////////////////////////////////////////////
 // Sequential Logic
 /////////////////////////////////////////////////////
 // Data Wishbone interface
 always @(posedge clk_i `CFG_RESET_SENSITIVITY)
 begin
     if (rst_i == `TRUE)
     begin
         d_cyc_o <= `FALSE;
         d_stb_o <= `FALSE;
         d_dat_o <= {`LM32_WORD_WIDTH{1'b0}};
         d_adr_o <= {`LM32_WORD_WIDTH{1'b0}};
         d_sel_o <= {`LM32_BYTE_SELECT_WIDTH{`FALSE}};
         d_we_o <= `FALSE;
         d_cti_o <= `LM32_CTYPE_END;
         d_lock_o <= `FALSE;
         wb_data_m <= {`LM32_WORD_WIDTH{1'b0}};
         wb_load_complete <= `FALSE;
         stall_wb_load <= `FALSE;
 `ifdef CFG_DCACHE_ENABLED
         dcache_refill_ready <= `FALSE;
 `endif
     end
     else
     begin
 `ifdef CFG_DCACHE_ENABLED
         // Refill ready should only be asserted for a single cycle
         dcache_refill_ready <= `FALSE;
 `endif
         // Is a Wishbone cycle already in progress?
         if (d_cyc_o == `TRUE)
         begin
             // Is the cycle complete?
             if ((d_ack_i == `TRUE) || (d_err_i == `TRUE))
             begin
 `ifdef CFG_DCACHE_ENABLED
                 if ((dcache_refilling == `TRUE) && (!last_word))
                 begin
                     // Fetch next word of cache line
                     d_adr_o[addr_offset_msb:addr_offset_lsb] <= d_adr_o[addr_offset_msb:addr_offset_lsb] + 1'b1;
                 end
                 else
 `endif
                 begin
                     // Refill/access complete
                     d_cyc_o <= `FALSE;
                     d_stb_o <= `FALSE;
                     d_lock_o <= `FALSE;
                 end
 `ifdef CFG_DCACHE_ENABLED
                 d_cti_o <= next_cycle_type;
                 // If we are performing a refill, indicate to cache next word of data is ready
                 dcache_refill_ready <= dcache_refilling;
 `endif
                 // Register data read from Wishbone interface
                 wb_data_m <= d_dat_i;
                 // Don't set when stores complete - otherwise we'll deadlock if load in m stage
                 wb_load_complete <= !d_we_o;
             end
             // synthesis translate_off
             if (d_err_i == `TRUE)
                 $display ("Data bus error. Address: %x", d_adr_o);
             // synthesis translate_on
         end
         else
         begin
 `ifdef CFG_DCACHE_ENABLED
             if (dcache_refill_request == `TRUE)
             begin
                 // Start cache refill
                 d_adr_o <= first_address;
                 d_cyc_o <= `TRUE;
                 d_sel_o <= {`LM32_WORD_WIDTH/8{`TRUE}};
                 d_stb_o <= `TRUE;
                 d_we_o <= `FALSE;
                 d_cti_o <= first_cycle_type;
                 //d_lock_o <= `TRUE;
             end
             else
 `endif
                  if (   (store_q_m == `TRUE)
                      && (stall_m == `FALSE)
 `ifdef CFG_DRAM_ENABLED
                      && (dram_select_m == `FALSE)
 `endif
 `ifdef CFG_IROM_ENABLED
 		     && (irom_select_m == `FALSE)
 `endif
                     )
             begin
                 // Data cache is write through, so all stores go to memory
                 d_dat_o <= store_data_m;
                 d_adr_o <= load_store_address_m;
                 d_cyc_o <= `TRUE;
                 d_sel_o <= byte_enable_m;
                 d_stb_o <= `TRUE;
                 d_we_o <= `TRUE;
                 d_cti_o <= `LM32_CTYPE_END;
             end
             else if (   (load_q_m == `TRUE)
                      && (wb_select_m == `TRUE)
                      && (wb_load_complete == `FALSE)
                      // stall_m will be TRUE, because stall_wb_load will be TRUE
                     )
             begin
                 // Read requested address
                 stall_wb_load <= `FALSE;
                 d_adr_o <= load_store_address_m;
                 d_cyc_o <= `TRUE;
                 d_sel_o <= byte_enable_m;
                 d_stb_o <= `TRUE;
                 d_we_o <= `FALSE;
                 d_cti_o <= `LM32_CTYPE_END;
             end
         end
         // Clear load/store complete flag when instruction leaves M stage
         if (stall_m == `FALSE)
             wb_load_complete <= `FALSE;
         // When a Wishbone load first enters the M stage, we need to stall it
         if ((load_q_x == `TRUE) && (wb_select_x == `TRUE) && (stall_x == `FALSE))
             stall_wb_load <= `TRUE;
         // Clear stall request if load instruction is killed
         if ((kill_m == `TRUE) || (exception_m == `TRUE))
             stall_wb_load <= `FALSE;
     end
 end
 // Pipeline registers
 // X/M stage pipeline registers
 always @(posedge clk_i `CFG_RESET_SENSITIVITY)
 begin
     if (rst_i == `TRUE)
     begin
         sign_extend_m <= `FALSE;
         size_m <= 2'b00;
         byte_enable_m <= `FALSE;
         store_data_m <= {`LM32_WORD_WIDTH{1'b0}};
 `ifdef CFG_DCACHE_ENABLED
         dcache_select_m <= `FALSE;
 `endif
 `ifdef CFG_DRAM_ENABLED
         dram_select_m <= `FALSE;
 `endif
 `ifdef CFG_IROM_ENABLED
         irom_select_m <= `FALSE;
 `endif
         wb_select_m <= `FALSE;
     end
     else
     begin
         if (stall_m == `FALSE)
         begin
             sign_extend_m <= sign_extend_x;
             size_m <= size_x;
             byte_enable_m <= byte_enable_x;
             store_data_m <= store_data_x;
 `ifdef CFG_DCACHE_ENABLED
             dcache_select_m <= dcache_select_x;
 `endif
 `ifdef CFG_DRAM_ENABLED
             dram_select_m <= dram_select_x;
 `endif
 `ifdef CFG_IROM_ENABLED
             irom_select_m <= irom_select_x;
 `endif
             wb_select_m <= wb_select_x;
         end
     end
 end
 // M/W stage pipeline registers
 always @(posedge clk_i `CFG_RESET_SENSITIVITY)
 begin
     if (rst_i == `TRUE)
     begin
         size_w <= 2'b00;
         data_w <= {`LM32_WORD_WIDTH{1'b0}};
         sign_extend_w <= `FALSE;
     end
     else
     begin
         size_w <= size_m;
         data_w <= data_m;
         sign_extend_w <= sign_extend_m;
     end
 end
 /////////////////////////////////////////////////////
 // Behavioural Logic
 /////////////////////////////////////////////////////
 // synthesis translate_off
 // Check for non-aligned loads or stores
 always @(posedge clk_i)
 begin
     if (((load_q_m == `TRUE) || (store_q_m == `TRUE)) && (stall_m == `FALSE))
     begin
         if ((size_m === `LM32_SIZE_HWORD) && (load_store_address_m[0] !== 1'b0))
             $display ("Warning: Non-aligned halfword access. Address: 0x%0x Time: %0t.", load_store_address_m, $time);
         if ((size_m === `LM32_SIZE_WORD) && (load_store_address_m[1:0] !== 2'b00))
             $display ("Warning: Non-aligned word access. Address: 0x%0x Time: %0t.", load_store_address_m, $time);
     end
 end
 // synthesis translate_on
 endmodule

IPCores/lm32_cpu / annotate

lm32_load_store_unit.v@cd0b58aa6f83 (annotated)

lm32_load_store_unit.v