Fix a few scattered bugs, and get fetch to work.

[firearm.git] / Fetch.v

diff --git a/Fetch.v b/Fetch.v
new file mode 100644 (file)
index 0000000..0a18b31
--- /dev/null
+++ b/Fetch.v
@@ -0,0 +1,41 @@
+module Fetch(
+       input clk,
+       input Nrst,
+       
+       output wire [31:0] rd_addr,
+       output wire rd_req,
+       input rd_wait,
+       input [31:0] rd_data,
+       
+       input stall,
+       input jmp,
+       input [31:0] jmppc,
+       output wire bubble,
+       output wire [31:0] insn,
+       output reg [31:0] pc);
+
+       reg [31:0] prevpc;
+       initial
+               prevpc = 32'hFFFFFFFC;  /* ugh... the first pc we request will be this +4 */
+       always @(negedge Nrst)
+               prevpc <= 32'hFFFFFFFC;
+       
+       always @(*)
+               if (!Nrst)
+                       pc = 32'hFFFFFFFC;
+               else if (stall) /* don't change any internal state */
+                       pc = prevpc;
+               else if (jmp)
+                       pc = jmppc;
+               else
+                       pc = prevpc + 32'h4;
+       
+       assign bubble = stall | rd_wait;
+       assign rd_addr = pc;
+       assign rd_req = !stall;
+       assign insn = rd_data;
+                       
+       always @(posedge clk)
+               if (!rd_wait || !Nrst)
+                       prevpc <= pc;
+endmodule