make a git repo

1 files changed, 51 insertions, 0 deletions

diff --git a/fsm.v b/fsm.v
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+`timescale 1ns / 1ps
+// FSM module
+//
+// drives the data path through multiple cycles
+
+module fsm(
+  output [3:0] state,
+  input [2:0] instrtype,
+  input rst,
+  input clk
+);
+
+`include "params.v"
+
+reg [3:0] state, nextstate;
+
+always @(*) begin
+  if (rst) begin
+    nextstate = FETCH;
+  end else begin
+    case (state)
+      FETCH: nextstate = DECODE;
+      DECODE: if (instrtype == IINSTR || instrtype == RINSTR)
+                nextstate = ALUOP;
+              else if (instrtype == MEMRINSTR || instrtype == MEMWINSTR)
+                nextstate = MEMCALC;
+              else if (instrtype == BRINSTR)
+                nextstate = BRANCH;
+              else if (instrtype == JINSTR)
+                nextstate = JUMP;
+      MEMCALC: if (instrtype == MEMWINSTR)
+                 nextstate = MEMWRITE;
+               else if (instrtype == MEMRINSTR)
+                  nextstate = MEMREAD;
+      MEMWRITE: nextstate = FETCH;
+      MEMREAD: nextstate = MEMSTORE;
+      MEMSTORE: nextstate <= FETCH;
+      ALUOP: nextstate = ALUSTORE;
+      ALUSTORE: nextstate = FETCH;
+      BRANCH: nextstate = FETCH;
+      JUMP: nextstate = FETCH;
+    endcase
+  end
+end
+
+always @(posedge clk or posedge rst) begin
+  state <= rst ? FETCH : nextstate;
+end
+
+endmodule
+