amamory-verification / hw-formal-verif

Hardware Formal Verification

Formal Hardware Verification

This repository containts the assignements for the course Functional Verification on Digital Systems II, from the Graduate Program of Computer Science at PUCRS University.

These assignments are divided in three levels:

• Tutorial level: which is a step-by-step tutorial to help the students to know the tools and their setup. See the directory xtea-cripto-core for more.
• Entry Level: correspond to very basic designs, suggested as an initial steps for the students to build their own FV environments. See the vending-machine and formal-verif-book dircs for more.
• Master Level: correspond to the main assignment of the semester, which is more challenging. It is a Hemes router for networks-on-chip. See the noc-router dir for more.

For more information, refer to the Moodle webpage.

hw-formal-verif's Issues

Coin counter resets on overflow

V4:

When adding a coin with the coin counter at max (=0x1F), the coin counter resets, as shown in the attached picture.

Possible solution: returning the newly inserted coin

1. switch no a special state
   ...
elsif m100 = '1' then
if count < MAX_COUNT then pe <= soma;
   else pe <= devolve2;
   end if; else ...`

2. update D100 to reflect the special case
   d100 <= '1' when (ea = devolve or ea = devolve2) else '0';

3. add the new state to the state enumeration
   type state is (action, soma, sgreen, satum, sbacon, nulo, devolve, devolve2);

4. create a new constant (for the sake of readability)
   constant MAX_COUNT : integer := 2**(count'length)-1;

    		else
   

Wrong state transition when requesting multiple sandwiches.

Machine V4:

According to the specification, the machine should go to an error state when requesting multiple sandwiches at the same time. However, such constraint is violated when a coin is inserted along with requesting two sandwiches, as seen in the attached picture.

Possible solution: rearrange the following code to test error cases before accepting a coin.

if m100 = '1' then
pe <= soma;
elsif dev = '1' or (r_bacon = '1' and r_atum = '1') or (r_bacon = '1' and r_green = '1') or (r_atum = '1' and r_green = '1') then
pe <= nulo;
...

When it could be...

if dev = '1' or (r_bacon = '1' and r_atum = '1') or (r_bacon = '1' and r_green = '1') or (r_atum = '1' and r_green = '1') then
pe <= nulo;
elsif m100 = '1' then
pe <= soma;
...