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module icache
#(parameter AWIDTH=14,
parameter CWIDTH=6)
(input wb_clk_i,
input wb_rst_i,
input [AWIDTH-1:0] iwb_adr_i,
input iwb_stb_i,
output [31:0] iwb_dat_o,
output iwb_ack_o,
input [31:0] iram_dat_i,
output [AWIDTH-1:0] iram_adr_o,
output iram_en_o );
localparam TAGWIDTH = AWIDTH-CWIDTH-2;
reg stb_d1, ack_d1, miss_d1;
reg [AWIDTH-1:0] held_addr;
reg [31:0] idata [0:(1<<CWIDTH)-1];
reg [TAGWIDTH-1:0] itags [0:(1<<CWIDTH)-1];
reg ivalid [0:(1<<CWIDTH)-1];
wire [CWIDTH-1:0] rd_line, wr_line;
wire [TAGWIDTH-1:0] wr_tags;
wire store_in_cache;
// /////////////////////////////////////
// Write into cache
integer i;
always @(posedge wb_clk_i)
if(wb_rst_i)
for(i=0;i<(1<<CWIDTH);i=i+1)
ivalid[i] <= 0;
else
if(store_in_cache)
ivalid[wr_line] <= 1'b1;
always @(posedge wb_clk_i)
if(store_in_cache)
begin
idata[wr_line] <= iram_dat_i;
itags[wr_line] <= wr_tags;
end
// //////////////////////////////////////
// Read from Cache
wire [TAGWIDTH-1:0] tag_out = itags[rd_line];
wire valid_out = ivalid[rd_line];
wire [31:0] data_out = idata[rd_line];
wire cache_hit = valid_out & (tag_out == iwb_adr_i[AWIDTH-1:CWIDTH+2]);
wire cache_miss = ~cache_hit;
// //////////////////////////////////////
// Handle 1-cycle delay of Block-RAM
always @(posedge wb_clk_i)
if(wb_rst_i)
stb_d1 <= 0;
else
stb_d1 <= iwb_stb_i;
always @(posedge wb_clk_i)
if(wb_rst_i)
held_addr <= 0;
else
held_addr <= iwb_adr_i;
always @(posedge wb_clk_i)
if(wb_rst_i)
ack_d1 <= 1'b0;
else
ack_d1 <= iwb_ack_o;
always @(posedge wb_clk_i)
if(wb_rst_i)
miss_d1 <= 0;
else
miss_d1 <= cache_miss;
//`define IC_NOCACHE
//`define IC_BASIC
//`define IC_FORWARDING_DP
`define IC_FORWARDING_SP
//`define IC_PREFETCH
`ifdef IC_NOCACHE
assign iwb_dat_o = iram_dat_i;
assign iwb_ack_o = iwb_stb_i & (stb_d1 & ~ack_d1);
assign iram_adr_o = iwb_adr_i;
assign iram_en_o = 1'b1;
assign rd_line = 0;
assign wr_line = 0;
assign wr_tags = 0;
assign store_in_cache = 0;
`endif
`ifdef IC_BASIC // Very basic, no forwarding, 2 wait states on miss
assign iwb_dat_o = data_out;
assign iwb_ack_o = iwb_stb_i & cache_hit;
assign iram_adr_o = iwb_adr_i;
assign iram_en_o = 1'b1;
assign rd_line = iwb_adr_i[CWIDTH+1:2];
assign wr_line = rd_line;
assign wr_tags = iwb_adr_i[AWIDTH-1:CWIDTH+2];
assign store_in_cache = stb_d1 & miss_d1;
`endif
`ifdef IC_FORWARDING_DP // Simple forwarding, 1 wait state on miss, dual-port ram
assign iwb_dat_o = cache_hit ? data_out : iram_dat_i;
assign iwb_ack_o = iwb_stb_i & (cache_hit | (stb_d1 & ~ack_d1));
assign iram_adr_o = iwb_adr_i;
assign iram_en_o = 1'b1;
assign rd_line = iwb_adr_i[CWIDTH+1:2];
assign wr_line = held_addr[CWIDTH+1:2];
assign wr_tags = held_addr[AWIDTH-1:CWIDTH+2];
assign store_in_cache = iwb_stb_i & stb_d1 & miss_d1 & ~ack_d1;
`endif
`ifdef IC_FORWARDING_SP // Simple forwarding, 1 wait state on miss, single-port ram
assign iwb_dat_o = cache_hit ? data_out : iram_dat_i;
assign iwb_ack_o = iwb_stb_i & (cache_hit | (stb_d1 & ~ack_d1));
assign iram_adr_o = iwb_adr_i;
assign iram_en_o = 1'b1;
assign rd_line = iwb_adr_i[CWIDTH+1:2];
assign wr_line = rd_line;
assign wr_tags = iwb_adr_i[AWIDTH-1:CWIDTH+2];
assign store_in_cache = iwb_stb_i & stb_d1 & miss_d1 & ~ack_d1;
`endif
`ifdef IC_PREFETCH // Forwarding plus prefetch
`endif
endmodule // icache
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