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-rw-r--r--src/rtl/rosc_entropy.v2
-rw-r--r--src/rtl/rosc_entropy_core.v57
2 files changed, 47 insertions, 12 deletions
diff --git a/src/rtl/rosc_entropy.v b/src/rtl/rosc_entropy.v
index 0a7e60b..77af1f5 100644
--- a/src/rtl/rosc_entropy.v
+++ b/src/rtl/rosc_entropy.v
@@ -141,7 +141,7 @@ module rosc_entropy(
.clk(clk),
.reset_n(reset_n),
- .en(enable_reg),
+ .enable(enable_reg),
.opa(op_a_reg),
.opb(op_b_reg),
diff --git a/src/rtl/rosc_entropy_core.v b/src/rtl/rosc_entropy_core.v
index cd70f8a..4a43eb9 100644
--- a/src/rtl/rosc_entropy_core.v
+++ b/src/rtl/rosc_entropy_core.v
@@ -40,7 +40,7 @@ module rosc_entropy_core(
input wire clk,
input wire reset_n,
- input wire en,
+ input wire enable,
input wire [31 : 0] opa,
input wire [31 : 0] opb,
@@ -60,6 +60,8 @@ module rosc_entropy_core(
//----------------------------------------------------------------
// Parameters.
//----------------------------------------------------------------
+ // 100000 cycles warmup delay.
+ localparam WARMUP_CYCLES = 24'h0186a0;
localparam ADDER_WIDTH = 1;
localparam DEBUG_DELAY = 32'h002c4b40;
localparam NUM_SHIFT_BITS = 8'h20;
@@ -69,6 +71,11 @@ module rosc_entropy_core(
//----------------------------------------------------------------
// Registers including update variables and write enable.
//----------------------------------------------------------------
+ reg [23 : 0] warmup_cycle_ctr_reg;
+ reg [23 : 0] warmup_cycle_ctr_new;
+ reg warmup_cycle_ctr_we;
+ reg warmup_done;
+
reg [31 : 0] ent_shift_reg;
reg [31 : 0] ent_shift_new;
reg ent_shift_we;
@@ -117,7 +124,7 @@ module rosc_entropy_core(
assign rosc_outputs = rosc_dout;
assign raw_entropy = ent_shift_reg;
assign entropy_data = entropy_reg;
- assign entropy_valid = entropy_valid_reg;
+ assign entropy_valid = entropy_valid_reg & warmup_done;
assign debug = debug_reg;
@@ -155,20 +162,24 @@ module rosc_entropy_core(
begin
if (!reset_n)
begin
- ent_shift_reg <= 32'h00000000;
- entropy_reg <= 32'h00000000;
- entropy_valid_reg <= 0;
- bit_ctr_reg <= 8'h00;
- sample_ctr_reg <= 8'h00;
- debug_delay_ctr_reg <= 32'h00000000;
- debug_reg <= 8'h00;
- debug_update_reg <= 0;
+ ent_shift_reg <= 32'h00000000;
+ entropy_reg <= 32'h00000000;
+ entropy_valid_reg <= 0;
+ bit_ctr_reg <= 8'h00;
+ sample_ctr_reg <= 8'h00;
+ debug_delay_ctr_reg <= 32'h00000000;
+ warmup_cycle_ctr_reg <= WARMUP_CYCLES;
+ debug_reg <= 8'h00;
+ debug_update_reg <= 0;
end
else
begin
sample_ctr_reg <= sample_ctr_new;
debug_update_reg <= debug_update;
+ if (warmup_cycle_ctr_we)
+ warmup_cycle_ctr_reg <= warmup_cycle_ctr_new;
+
if (ent_shift_we)
begin
ent_shift_reg <= ent_shift_new;
@@ -229,6 +240,30 @@ module rosc_entropy_core(
//----------------------------------------------------------------
+ // warmup_ctr
+ //
+ // Logic for the warmup counter. This counter starts
+ // decreasing when reset lifts and decreases until reaching zero.
+ // At zero the counter stops and asserts warmup_done.
+ //----------------------------------------------------------------
+ always @*
+ begin : warmup_ctr
+ if (warmup_cycle_ctr_reg == 0)
+ begin
+ warmup_cycle_ctr_new = 24'h000000;
+ warmup_cycle_ctr_we = 0;
+ warmup_done = 1;
+ end
+ else
+ begin
+ warmup_cycle_ctr_new = warmup_cycle_ctr_reg - 1'b1;
+ warmup_cycle_ctr_we = 1;
+ warmup_done = 0;
+ end
+ end
+
+
+ //----------------------------------------------------------------
// entropy_out
//
// Logic that implements the random output control. If we have
@@ -289,7 +324,7 @@ module rosc_entropy_core(
sample_ctr_new = sample_ctr_reg + 1'b1;
- if (en && (sample_ctr_reg == SAMPLE_CLK_CYCLES))
+ if (enable && warmup_done && (sample_ctr_reg == SAMPLE_CLK_CYCLES))
begin
sample_ctr_new = 8'h00;
bit_ctr_inc = 1;