// =============================================================================
// 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.
//
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// 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 : 6.0.13
// =============================================================================
`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_q_x,
load_q_m,
store_q_m,
sign_extend_x,
size_x,
`ifdef CFG_DCACHE_ENABLED
dflush,
`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
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_width = 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_q_x; // Load 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
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
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
wire [`LM32_CTYPE_RNG] d_cti_o;
output d_lock_o; // Date Wishbone interface lock bus
wire 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 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;
wire [`LM32_WORD_RNG] dram_data_m; // Data read from data RAM
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
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
/////////////////////////////////////////////////////
`define INCLUDE_FUNCTION
`include "lm32_functions.v"
/////////////////////////////////////////////////////
// Instantiations
/////////////////////////////////////////////////////
`ifdef CFG_DRAM_ENABLED
// Data RAM
pmi_ram_dp_true #(
// ----- Parameters -------
.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_regmode_a ("noreg"),
.pmi_regmode_b ("noreg"),
.pmi_gsr ("enable"),
.pmi_resetmode ("async"),
.pmi_init_file (`CFG_DRAM_INIT_FILE),
.pmi_init_file_format ("hex"),
.module_type ("pmi_ram_dp")
) 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),
.ClockEnB (!stall_m),
.WrA (`FALSE),
.WrB (store_q_m),
// ----- Outputs -------
.QA (dram_data_m),
.QB ()
);
`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),
.store_data (store_data_m),
.store_byte_select (byte_enable_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_DCACHE_ENABLED
assign dcache_select_x = (load_store_address_x >= `CFG_DCACHE_BASE_ADDRESS) && (load_store_address_x <= `CFG_DCACHE_LIMIT);
//assign dcache_select_x = (load_store_address_x >= `CFG_DCACHE_BASE_ADDRESS) && ~|load_store_address_x[`LM32_WORD_WIDTH-1:clogb2(`CFG_DCACHE_LIMIT-`CFG_DCACHE_BASE_ADDRESS)-1];
`endif
`ifdef CFG_DRAM_ENABLED
assign dram_select_x = (load_store_address_x >= `CFG_DRAM_BASE_ADDRESS) && (load_store_address_x <= `CFG_DRAM_LIMIT);
`endif
assign wb_select_x = `TRUE
`ifdef CFG_DCACHE_ENABLED
&& !dcache_select_x
`endif
`ifdef CFG_DRAM_ENABLED
&& !dram_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
// Select data from selected source
`ifdef CFG_DCACHE_ENABLED
`ifdef CFG_DRAM_ENABLED
assign data_m = wb_select_m == `TRUE
? wb_data_m
: dram_select_m == `TRUE
? dram_data_m
: dcache_data_m;
`else
assign data_m = wb_select_m == `TRUE ? wb_data_m : dcache_data_m;
`endif
`else
`ifdef CFG_DRAM_ENABLED
assign data_m = wb_select_m == `TRUE ? wb_data_m : dram_data_m;
`else
assign data_m = wb_data_m;
`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 Wishbone signals
assign d_cti_o = `LM32_CTYPE_WIDTH'd0;
assign d_lock_o = `FALSE;
assign d_bte_o = `LM32_BTYPE_WIDTH'd0;
`ifdef CFG_DCACHE_ENABLED
// Generate signal to indicate last word in cache line
generate
if (bytes_per_line > 4)
begin
assign first_address = {dcache_refill_address[`LM32_WORD_WIDTH-1:addr_offset_msb+1], {addr_offset_width{1'b0}}, 2'b00};
assign last_word = (&d_adr_o[addr_offset_msb:addr_offset_lsb]) == 1'b1;
end
else
begin
assign first_address = {dcache_refill_address[`LM32_WORD_WIDTH-1:2], 2'b00};
assign last_word = `TRUE;
end
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;
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;
end
`ifdef CFG_DCACHE_ENABLED
// 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;
end
else
`endif
if ( (store_q_m == `TRUE)
&& (stall_m == `FALSE)
`ifdef CFG_DRAM_ENABLED
&& !dram_select_m
`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;
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;
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
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
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
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