Honored Contributor
Honored ContributorThe credits will have to be returned to your PCIe board from the system. The amount of time it takes to get credits back will be system dependent. Just a datapoint...on the system that I am using, I observed a read request to completion latency of ~500ns. So, in my case, credits could not come back faster than 500ns from the time I sent a transmit request.
Another note, the following thread mentions that the PCIe specification does not require flow control information to be updated when a malformed TLP is sent. I have not personally verified this in the spec, but assuming this to be true, if you sent a malformed request, you may have eaten your credits up and created a lockup. http://www.alteraforum.com/forum/showthread.php?t=18801&highlight=pcie+lockup Unfortunately, we are starting to get into PCIe system behavior, which I am a lilttle sketchy on...still learning myself.
