From 559bbd966c816374f0e47ce5c28039cc74c605c4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Joachim=20Stro=CC=88mbergson?= <joachim@secworks.se>
Date: Sat, 18 Jul 2015 08:55:49 +0200
Subject: Simplified the pointer handling. Fixed size of counter. Now all
positions in the fifo is used and flags are correctly set.
---
src/rtl/trng_csprng_fifo.v | 179 +++++++++++++++++++++++----------------------
1 file changed, 90 insertions(+), 89 deletions(-)
(limited to 'src')
diff --git a/src/rtl/trng_csprng_fifo.v b/src/rtl/trng_csprng_fifo.v
index 1f91802..e90d23d 100644
--- a/src/rtl/trng_csprng_fifo.v
+++ b/src/rtl/trng_csprng_fifo.v
@@ -56,11 +56,12 @@ module trng_csprng_fifo(
// Internal constant and parameter definitions.
//----------------------------------------------------------------
localparam FIFO_ADDR_BITS = 2;
- localparam FIFO_ADDR_MAX = FIFO_ADDR_BITS - 1;
- localparam FIFO_MAX = (2 ** FIFO_ADDR_BITS) - 1;
+ localparam FIFO_ADDR_MAX = (2**FIFO_ADDR_BITS) - 1;
+ localparam FIFO_MAX = (2 ** FIFO_ADDR_BITS);
localparam WR_IDLE = 0;
- localparam WR_STORE = 1;
+ localparam WR_WAIT = 1;
+ localparam WR_NEXT = 2;
localparam WR_DISCARD = 7;
localparam RD_IDLE = 0;
@@ -71,7 +72,7 @@ module trng_csprng_fifo(
//----------------------------------------------------------------
// Registers including update variables and write enable.
//----------------------------------------------------------------
- reg [511 : 0] fifo_mem [0 : FIFO_MAX];
+ reg [511 : 0] fifo_mem [0 : FIFO_ADDR_MAX];
reg fifo_mem_we;
reg [3 : 0] mux_data_ptr_reg;
@@ -80,26 +81,26 @@ module trng_csprng_fifo(
reg mux_data_ptr_rst;
reg mux_data_ptr_we;
- reg [FIFO_ADDR_MAX : 0] rd_ptr_reg;
- reg [FIFO_ADDR_MAX : 0] rd_ptr_new;
- reg rd_ptr_inc;
- reg rd_ptr_rst;
- reg rd_ptr_we;
-
- reg [FIFO_ADDR_MAX : 0] wr_ptr_reg;
- reg [FIFO_ADDR_MAX : 0] wr_ptr_new;
- reg wr_ptr_inc;
- reg wr_ptr_rst;
- reg wr_ptr_we;
-
- reg [FIFO_ADDR_MAX : 0] fifo_ctr_reg;
- reg [FIFO_ADDR_MAX : 0] fifo_ctr_new;
- reg fifo_ctr_inc;
- reg fifo_ctr_dec;
- reg fifo_ctr_rst;
- reg fifo_ctr_we;
- reg fifo_empty;
- reg fifo_full;
+ reg [(FIFO_ADDR_BITS - 1) : 0] rd_ptr_reg;
+ reg [(FIFO_ADDR_BITS - 1) : 0] rd_ptr_new;
+ reg rd_ptr_inc;
+ reg rd_ptr_rst;
+ reg rd_ptr_we;
+
+ reg [(FIFO_ADDR_BITS - 1) : 0] wr_ptr_reg;
+ reg [(FIFO_ADDR_BITS - 1) : 0] wr_ptr_new;
+ reg wr_ptr_inc;
+ reg wr_ptr_rst;
+ reg wr_ptr_we;
+
+ reg [FIFO_ADDR_BITS : 0] fifo_ctr_reg;
+ reg [FIFO_ADDR_BITS : 0] fifo_ctr_new;
+ reg fifo_ctr_inc;
+ reg fifo_ctr_dec;
+ reg fifo_ctr_rst;
+ reg fifo_ctr_we;
+ reg fifo_empty;
+ reg fifo_full;
reg [31 : 0] rnd_data_reg;
@@ -117,6 +118,7 @@ module trng_csprng_fifo(
reg more_data_reg;
reg more_data_new;
+ reg more_data_we;
//----------------------------------------------------------------
@@ -147,8 +149,8 @@ module trng_csprng_fifo(
fifo_mem[02] <= {16{32'h00000000}};
fifo_mem[03] <= {16{32'h00000000}};
mux_data_ptr_reg <= 4'h0;
- rd_ptr_reg <= {FIFO_ADDR_BITS{1'b0}};
- wr_ptr_reg <= {FIFO_ADDR_BITS{1'b0}};
+ rd_ptr_reg <= {(FIFO_ADDR_BITS - 1){1'b0}};
+ wr_ptr_reg <= {(FIFO_ADDR_BITS - 1){1'b0}};
fifo_ctr_reg <= {FIFO_ADDR_BITS{1'b0}};
rnd_data_reg <= 32'h00000000;
rnd_syn_reg <= 0;
@@ -158,48 +160,34 @@ module trng_csprng_fifo(
end
else
begin
- rnd_data_reg <= muxed_data;
- more_data_reg <= more_data_new;
+ rnd_data_reg <= muxed_data;
+
+ if (more_data_we)
+ more_data_reg <= more_data_new;
if (rnd_syn_we)
- begin
- rnd_syn_reg <= rnd_syn_new;
- end
+ rnd_syn_reg <= rnd_syn_new;
if (fifo_mem_we)
- begin
- fifo_mem[wr_ptr_reg] <= csprng_data;
- end
+ fifo_mem[wr_ptr_reg] <= csprng_data;
if (mux_data_ptr_we)
- begin
- mux_data_ptr_reg <= mux_data_ptr_new;
- end
+ mux_data_ptr_reg <= mux_data_ptr_new;
if (rd_ptr_we)
- begin
- rd_ptr_reg <= rd_ptr_new;
- end
+ rd_ptr_reg <= rd_ptr_new;
if (wr_ptr_we)
- begin
- wr_ptr_reg <= wr_ptr_new;
- end
+ wr_ptr_reg <= wr_ptr_new;
if (fifo_ctr_we)
- begin
- fifo_ctr_reg <= fifo_ctr_new;
- end
+ fifo_ctr_reg <= fifo_ctr_new;
if (rd_ctrl_we)
- begin
- rd_ctrl_reg <= rd_ctrl_new;
- end
+ rd_ctrl_reg <= rd_ctrl_new;
if (wr_ctrl_we)
- begin
- wr_ctrl_reg <= wr_ctrl_new;
- end
+ wr_ctrl_reg <= wr_ctrl_new;
end
end // reg_update
@@ -257,18 +245,16 @@ module trng_csprng_fifo(
fifo_ctr_dec = 0;
if (rd_ptr_rst)
- rd_ptr_we = 1;
+ begin
+ rd_ptr_new = {FIFO_ADDR_BITS{1'b0}};
+ rd_ptr_we = 1;
+ end
if (rd_ptr_inc)
begin
- fifo_ctr_dec = 1;
- if (rd_ptr_reg == FIFO_MAX)
- rd_ptr_we = 1;
- else
- begin
- rd_ptr_new = rd_ptr_reg + 1'b1;
- rd_ptr_we = 1;
- end
+ fifo_ctr_dec = 1;
+ rd_ptr_new = rd_ptr_reg + 1'b1;
+ rd_ptr_we = 1;
end
end // fifo_rd_ptr
@@ -280,21 +266,21 @@ module trng_csprng_fifo(
//----------------------------------------------------------------
always @*
begin : fifo_wr_ptr
- wr_ptr_new = {FIFO_ADDR_BITS{1'b0}};
- wr_ptr_we = 0;
+ wr_ptr_new = {FIFO_ADDR_BITS{1'b0}};
+ wr_ptr_we = 0;
+ fifo_ctr_inc = 0;
if (wr_ptr_rst)
- wr_ptr_we = 1;
+ begin
+ wr_ptr_new = {FIFO_ADDR_BITS{1'b0}};
+ wr_ptr_we = 1;
+ end
if (wr_ptr_inc)
begin
- if (wr_ptr_reg == FIFO_MAX)
- wr_ptr_we = 1;
- else
- begin
- wr_ptr_new = wr_ptr_reg + 1'b1;
- wr_ptr_we = 1;
- end
+ fifo_ctr_inc = 1;
+ wr_ptr_new = wr_ptr_reg + 1'b1;
+ wr_ptr_we = 1;
end
end // fifo_wr_ptr
@@ -326,15 +312,18 @@ module trng_csprng_fifo(
end
if (fifo_ctr_rst)
- fifo_ctr_we = 1;
+ begin
+ fifo_ctr_new = {FIFO_ADDR_BITS{1'b0}};
+ fifo_ctr_we = 1;
+ end
- if ((fifo_ctr_inc) && (fifo_ctr_reg < FIFO_MAX))
+ if (fifo_ctr_inc)
begin
fifo_ctr_new = fifo_ctr_reg + 1'b1;
fifo_ctr_we = 1;
end
- if ((fifo_ctr_dec) && (fifo_ctr_reg > 0))
+ if (fifo_ctr_dec)
begin
fifo_ctr_new = fifo_ctr_reg - 1'b1;
fifo_ctr_we = 1;
@@ -429,9 +418,9 @@ module trng_csprng_fifo(
wr_ptr_inc = 0;
wr_ptr_rst = 0;
fifo_mem_we = 0;
- fifo_ctr_inc = 0;
fifo_ctr_rst = 0;
more_data_new = 0;
+ more_data_we = 0;
wr_ctrl_new = WR_IDLE;
wr_ctrl_we = 0;
@@ -448,31 +437,43 @@ module trng_csprng_fifo(
if (!fifo_full)
begin
more_data_new = 1'b1;
+ more_data_we = 1'b1;
+ wr_ctrl_new = WR_WAIT;
+ wr_ctrl_we = 1;
end
-
- if (csprng_data_valid)
+ else
begin
- wr_ctrl_new = WR_STORE;
- wr_ctrl_we = 1;
+ more_data_new = 1'b0;
+ more_data_we = 1'b1;
end
end
end
- WR_STORE:
+ WR_WAIT:
begin
- fifo_mem_we = 1;
- wr_ptr_inc = 1;
- fifo_ctr_inc = 1;
- wr_ctrl_new = WR_IDLE;
- wr_ctrl_we = 1;
+ if (csprng_data_valid)
+ begin
+ fifo_mem_we = 1;
+ wr_ptr_inc = 1;
+ wr_ctrl_new = WR_NEXT;
+ wr_ctrl_we = 1;
+ end
+ end
+
+ WR_NEXT:
+ begin
+ more_data_new = 1'b0;
+ more_data_we = 1'b1;
+ wr_ctrl_new = WR_IDLE;
+ wr_ctrl_we = 1;
end
WR_DISCARD:
begin
- fifo_ctr_rst = 1;
- wr_ptr_rst = 1;
- wr_ctrl_new = WR_IDLE;
- wr_ctrl_we = 1;
+ fifo_ctr_rst = 1;
+ wr_ptr_rst = 1;
+ wr_ctrl_new = WR_IDLE;
+ wr_ctrl_we = 1;
end
endcase // case (wr_ctrl_reg)
end // wr_ctrl
--
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