Add icache kind of

diff --git a/icache.v b/icache.v
new file mode 100644 (file)
index 0000000..e441e20
--- /dev/null
+++ b/icache.v
@@ -0,0 +1,33 @@
+/* 16 cache entries, 64-byte long cache lines */
+
+module ICache(
+       input clk,
+       input [31:0] rd_addr,
+       input rd_req,
+       output reg rd_wait,
+       output reg [31:0] rd_data);
+       
+       /* [31 tag 11] [10 cache index 7] [5 data index 0]
+        * so the data index is 6 bits long
+        * so the cache index is 4 bits long
+        * so the tag is 21 bits long. c.c
+        */
+       
+       reg cache_valid [15:0];
+       reg [20:0] cache_tags [15:0];
+       reg [31:0] cache_data [15:0] [7:0];
+       
+       initial
+               for (i = 0; i < 16; i = i + 1)
+                       cache_valid[i] <= 0;
+       
+       wire [5:0] rd_didx = rd_addr[5:0];
+       wire [3:0] rd_didx_word = rd_didx[5:2];
+       wire [3:0] rd_idx = rd_addr[10:7];
+       wire [20:0] rd_tag = rd_addr[31:11];
+       
+       always @(*) begin       /* XXX does this work nowadays? */
+               rd_wait = !(cache_valid[rd_idx] && (cache_tags[rd_idx] == rd_tag));
+               rd_data = cache_data[rd_idx][rd_didx_word];
+       end
+endmodule