Connected the pipeline regs for t1 and t2 in the stat update logic. Verified functionality. Updated README after test implementation. The design now meets 100 MHz clock in Artix7 with speed grade -1.

3 files changed, 30 insertions, 13 deletions

diff --git a/README.md b/README.md
index 79f17f5..1790058 100644
--- a/README.md
+++ b/README.md
@@ -74,6 +74,19 @@ Implementation results using Altera Quartus-II 13.1.
 - 66 cycles latency
 
 
+### Xilinx Artix-7 FPGAs ###
+Implementation results using Xilinx ISE 14.7
+This implementation includes pipeline regsisters.
+
+- xc7a200t-1fbg484
+- 2229 Slice LUTs
+- 775 Slices
+- 1935 registers
+- 101 MHz
+- 130 cycles latency
+
+
+
 ## TODO ##
 - Extensive verification in physical device.
 - Complete documentation.
diff --git a/src/rtl/sha256_core.v b/src/rtl/sha256_core.v
index 95ad28b..048df2b 100644
--- a/src/rtl/sha256_core.v
+++ b/src/rtl/sha256_core.v
@@ -135,7 +135,10 @@ module sha256_core(
   reg          H_we;
 
   reg [31 : 0] t1_reg;
+  reg [31 : 0] t1_new;
+
   reg [31 : 0] t2_reg;
+  reg [31 : 0] t2_new;
 
   reg [5 : 0] t_ctr_reg;
   reg [5 : 0] t_ctr_new;
@@ -165,9 +168,6 @@ module sha256_core(
 
   reg ready_flag;
 
-  reg [31 : 0] t1;
-  reg [31 : 0] t2;
-
   wire [31 : 0] k_data;
 
   reg           w_init;
@@ -241,8 +241,8 @@ module sha256_core(
         end
       else
         begin
-          t1_reg <= t1;
-          t2_reg <= t2;
+          t1_reg <= t1_new;
+          t2_reg <= t2_new;
 
           if (a_h_we)
             begin
@@ -385,7 +385,7 @@ module sha256_core(
 
       ch = (e_reg & f_reg) ^ ((~e_reg) & g_reg);
 
-      t1 = h_reg + sum1 + ch + w_data + k_data;
+      t1_new = h_reg + sum1 + ch + w_data + k_data;
     end // t1_logic
 
 
@@ -405,7 +405,7 @@ module sha256_core(
 
       maj = (a_reg & b_reg) ^ (a_reg & c_reg) ^ (b_reg & c_reg);
 
-      t2 = sum0 + maj;
+      t2_new = sum0 + maj;
     end // t2_logic
 
 
@@ -425,11 +425,9 @@ module sha256_core(
       f_new  = 32'h0;
       g_new  = 32'h0;
       h_new  = 32'h0;
-      a_h_we = 1'h0;
 
       if (state_init)
         begin
-          a_h_we = 1'h1;
           if (first_block)
             begin
               if (mode)
@@ -470,15 +468,14 @@ module sha256_core(
 
       if (state_update)
         begin
-          a_new  = t1 + t2;
+          a_new  = t1_reg + t2_reg;
           b_new  = a_reg;
           c_new  = b_reg;
           d_new  = c_reg;
-          e_new  = d_reg + t1;
+          e_new  = d_reg + t1_reg;
           f_new  = e_reg;
           g_new  = f_reg;
           h_new  = g_reg;
-          a_h_we = 1'h1;
         end
     end // state_logic
 
@@ -519,6 +516,7 @@ module sha256_core(
       digest_update    = 1'h0;
       state_init       = 1'h0;
       state_update     = 1'h0;
+      a_h_we           = 1'h0;
       first_block      = 1'h0;
       ready_flag       = 1'h0;
       w_init           = 1'h0;
@@ -541,6 +539,7 @@ module sha256_core(
                 digest_init      = 1'h1;
                 w_init           = 1'h1;
                 state_init       = 1'h1;
+                a_h_we           = 1'h1;
                 first_block      = 1'h1;
                 t_ctr_rst        = 1'h1;
                 digest_valid_new = 1'h0;
@@ -553,6 +552,7 @@ module sha256_core(
               begin
                 w_init           = 1'h1;
                 state_init       = 1'h1;
+                a_h_we           = 1'h1;
                 t_ctr_rst        = 1'h1;
                 digest_valid_new = 1'h0;
                 digest_valid_we  = 1'h1;
@@ -561,8 +561,10 @@ module sha256_core(
               end
           end
 
+
         CTRL_ROUNDS0:
           begin
+            state_update    = 1'h1;
             sha256_ctrl_new = CTRL_ROUNDS1;
             sha256_ctrl_we  = 1'h1;
           end
@@ -572,6 +574,7 @@ module sha256_core(
           begin
             w_next       = 1'h1;
             state_update = 1'h1;
+            a_h_we       = 1'h1;
             t_ctr_inc    = 1'h1;
 
             if (t_ctr_reg == SHA256_ROUNDS)
diff --git a/src/tb/tb_sha256_core.v b/src/tb/tb_sha256_core.v
index 3b76aca..a037128 100644
--- a/src/tb/tb_sha256_core.v
+++ b/src/tb/tb_sha256_core.v
@@ -186,7 +186,8 @@ module tb_sha256_core();
 
       $display("State update values:");
       $display("w  = 0x%08x, k  = 0x%08x", dut.w_data, dut.k_data);
-      $display("t1 = 0x%08x, t2 = 0x%08x", dut.t1, dut.t2);
+      $display("t1_new = 0x%08x, t1_reg = 0x%08x, t2_new = 0x%08x, t2_reg = 0x%08x",
+               dut.t1_new, dut.t1_reg, dut.t2_new, dut.t2_reg);
       $display("");
     end
   endtask // dump_dut_state