Description
Memory read and write transaction may fail if the PCI Express® Device Identification Class Code Register is set to 0.
A class code of 0 is reserved for devices built before class code definitions were finalized (pre PCI™ 2.0). Consequently, this is an invalid Device Class for PCI Express.
Resolution
You can obtain valid Device Class codes from the PCI-SIG® PCI Code and ID Assignment Specification.