Answer Your Requests.

Of the "Big Five" - the PGNs that must be supported to be considered RV-C compliant, the Request for PGN seems to be the one that designers are most likely to implement incompletely. This PGN has more wide-ranging consequences that might appear at first glance.

There are two versions of this PGN. The address-specific version (PGN 0xEAxx, where xx is your node's source address) always requires a response. If the PGN is one that your node supports, your node responds with the appropriate data. If your PGN doesn't support that PGN, your node replies with a NAK (0xE9FF), with code 1.

But many requests are global, using PGN 0xEAFF. In this case, your node either responds with the requested data or it does nothing. It does not send the NAK.

What many designers forget is that your node must support requests for all PGNs that it ever broadcasts. It is not limited to just the DM1, PRODUCT_ID, or NAME PGNs.