added next_state concurrent assignment

src/socbridge_driver.vhd

@@ -72,6 +72,31 @@ begin
                         READ_RESPONSE when "01100",
                         NO_OP when others;
 
+    --- State Transition Diagram ---
+--                                                            
+--            +-----+                                         
+--           \|/    |                                         
+--          RESET --+                                         
+--            |                                               
+--            |                                               
+--          IDLE<-------------------+                 
+--          /  \                    |                            
+--         /     \                  |                            
+--        /       \                 |                            
+--      \|/       \|/               |                         
+--  TX_HEADER   RX_HEADER           |                        
+--       |           |              |                           
+--       |           |     ----+    |                           
+--      \|/         \|/   \|/  |    |                           
+--   TX_BODY     RX_RESPONSE---+    |                           
+--       |           |              |                           
+--       |  +--+     |              |                           
+--      \|/\|/ |    \|/             |                           
+--     TX_ACK--+ RX_BODY            |                           
+--       |           |              |                           
+--       |           |              |                           
+--       +-----------+--------------+                 
+--                                                            
     case curr_state is
       when IDLE => 
         if curr_command = WRITE or curr_command = WRITE_ADD then
@@ -82,12 +107,37 @@ begin
           next_state <= IDLE;
         end if;
       when RESET =>
+        next_state <= IDLE;
       when TX_HEADER =>
+      -- The header only takes one word (cycle) to transmit.
+      -- Continue to body directly afterwards. 
+        next_state <= TX_BODY;
       when TX_BODY =>
+      -- Here we want to stay in TX_BODY for the duration of a packet.
+      -- Right now, we transfer one single word at a time for simplicity
+        next_state <= TX_ACK;
       when TX_ACK =>
+      -- Wait for write acknowledgement. 
+        if curr_respoonse = WRITE_ACK then
+          next_state <= IDLE;
+        else 
+          next_state <= TX_ACK;
+        end if;
       when RX_HEADER =>
+      -- The header only takes one word (cycle) to transmit.
+      -- Continue to awaiting response directly afterwards.
+        next_state <= RX_RESPONSE;
       when RX_RESPONSE =>
+      -- Wait for read response. 
+        if curr_respoonse = READ_RESPONSE then
+          next_state <= RX_BODY;
+        else 
+          next_state <= RX_RESPONSE;
+        end if;
       when RX_BODY =>
+      -- Here we want to stay in RX_BODY for the duration of a packet.
+      -- Right now, we receive only one single word at a time for simplicity
+        next_state <= IDLE;
     end case;
   
   end process comb_proc;