What are some examples of protocol checking in monitor?

UVM
1

UVM suggests that we should put some protocol checking in monitor instead of scoreboard.
My question is what are some examples of protocol checking and what aren’t protocol checking?

Thanks.

2

That is a new recommendation to me. Protocol checking, such as making sure request is followed by grant, should be in the bus functional model / interface code that talks to the design signals. SVA are a good approach. Also, check for X and Z values here.

The monitor sees the final transaction values, and does not know the signal-level details, such as delays. The monitor sends the transactions (handles) to analysis components such as a scoreboard and coverage collector. The monitor should not be peeking at the transaction contents.

1 Like
3

Hi,

Few possible protocol checking examples:

  1. Few examples for AMBA AXI protocol:

    • READ Response is monitored for id which has no matching ongoing READ Request.
    • Burst type = WRAP enforces some rules on the possible length values. You can also classify it as “protocol check”.

  2. AMBA APB protocol:
    For READ transfers, the Requester must drive all bits of PSTRB LOW.

  3. A protocol which sends a packet(transaction) divided into few flits/segments(transfers) and has some info/meta-data/cmd fields which describes which segment is first one and which one is last one.
    For example: SOP (Start Of Packet) and EOP (End Of Packet).
    Each of 1bit width on the bus.
    Protocol rules:
    For the first segment SOP should be ‘1’.
    For the last segment EOP should be ‘1’.
    If packet has only a single segment/flit, than SOP=‘1’ && EOP=‘1’ for the same segment/flit.
    Segments of different packets should not be interleaved.
    Segments of same packet should be send in-order (meaning latter segments cannot bypass prior segments)
    Possible transactions monitored by the monitor which breaks the protocol: the first segment of the packet arrived with SOP=‘0’, and EOP=‘1’.
    Another illegal case, 2 segments arriving with SOP bit set for same packet, while no segment with EOP bit was set before arrival of the next segment with SOP bit set.
    Same case for 2 segments arriving with EOP bit set, without having the SOP bit set between them.

4

thanks michael