Initial commit.

vsrc/SRLatch.v

@@ -0,0 +1,22 @@
+// See LICENSE for license details.
+module SRLatch (
+  input set,
+  input reset,
+  output q
+);
+
+  reg latch;
+
+  // synopsys async_set_reset "set"
+  // synopsys one_hot "set, reset"
+  always @(set or reset)
+  begin
+    if (set)
+      latch <= 1'b1;
+    else if (reset)
+      latch <= 1'b0;
+  end
+
+  assign q = latch;
+
+endmodule

vsrc/vc707reset.v

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+// See LICENSE for license details.
+`timescale 1ns/1ps
+`default_nettype none
+`define RESET_SYNC 4
+`define DEBOUNCE_BITS 8
+
+module vc707reset(
+  // Asynchronous reset input, should be held high until
+  // all clocks are locked and power is stable.
+  input  wire areset,
+  // Clock domains are brought up in increasing order
+  // All clocks are reset for at least 2^DEBOUNCE_BITS * period(clock1)
+  input  wire clock1,
+  output wire reset1,
+  input  wire clock2,
+  output wire reset2,
+  input  wire clock3,
+  output wire reset3,
+  input  wire clock4,
+  output wire reset4
+);
+  sifive_reset_hold hold_clock0(areset, clock1, reset1);
+  sifive_reset_sync sync_clock2(reset1, clock2, reset2);
+  sifive_reset_sync sync_clock3(reset2, clock3, reset3);
+  sifive_reset_sync sync_clock4(reset3, clock4, reset4);
+endmodule
+
+// Assumes that areset is held for more than one clock
+// Allows areset to be deasserted asynchronously
+module sifive_reset_sync(
+  input  wire areset,
+  input  wire clock,
+  output wire reset
+);
+  reg [`RESET_SYNC-1:0] gen_reset = {`RESET_SYNC{1'b1}};
+  always @(posedge clock, posedge areset) begin
+    if (areset) begin
+      gen_reset <= {`RESET_SYNC{1'b1}};
+    end else begin
+      gen_reset <= {1'b0,gen_reset[`RESET_SYNC-1:1]};
+    end
+  end
+  assign reset = gen_reset[0];
+endmodule
+
+module sifive_reset_hold(
+  input  wire areset,
+  input  wire clock,
+  output wire reset
+);
+  wire raw_reset;
+  reg [`RESET_SYNC-1:0] sync_reset = {`RESET_SYNC{1'b1}};
+  reg [`DEBOUNCE_BITS:0] debounce_reset = {`DEBOUNCE_BITS{1'b1}};
+  wire out_reset;
+
+  // Captures reset even if clock is not running
+  sifive_reset_sync capture(areset, clock, raw_reset);
+
+  // Remove any glitches due to runt areset
+  always @(posedge clock) begin
+    sync_reset <= {raw_reset,sync_reset[`RESET_SYNC-1:1]};
+  end
+
+  // Debounce the reset
+  assign out_reset = debounce_reset[`DEBOUNCE_BITS];
+  always @(posedge clock) begin
+    if (sync_reset[0]) begin
+      debounce_reset <= {(`DEBOUNCE_BITS+1){1'b1}};
+    end else begin
+      debounce_reset <= debounce_reset - out_reset;
+    end
+  end
+
+  assign reset = out_reset;
+
+endmodule
+
+`default_nettype wire