IDT PCI Express 89HPES32NT24xG2, User Manual, Page: 271 / 744

IDT Non-Transparent Switch Operation
PES32NT24xG2 User Manual 14 - 23 January 30, 2013
Notes
• When ECRC checking is not enabled in the NT endpoint, there is a possibility of silent data
corruption on packets that cross the NTB (i.e., when a TLP with ECRC error is received by the
NT endpoint, the NT endpoint does not check ECRC, and a new ECRC is re-computed by the
NT endpoint in the destination partition, thereby “hiding” the existing error in the packet). To
prevent silent data corruption, it is strongly recommended that ECRC checking be enabled at
the NT endpoints.
– If ECRC checking is enabled in the NT endpoint that received the TLP (i.e., the ECRCCE bit is set
in the AERCTL register) and the TLP contains an ECRC error, then the ECRC associated with the
translated TLP is generated by recomputing the ECRC of the translated TLP and inverting all bits.
This ensures that the translated TLP carries a corrupt ECRC, so that the ECRC error may be
detected at the TLP’s final destination.
Also, if ECRC generation is enabled in an NT endpoint, then all TLPs originated by that endpoint contain
an ECRC. If ECRC generation is disabled in an NT endpoint, all TLPs emitted by the function do not have
ECRC.
Access Control Services (ACS)
The NT function supports the following ACS checks
1
:
– ACS Peer-to-Peer
2
Request Redirect
– ACS Peer-to-Peer Completion Redirect
– ACS Direct Translated Peer-to-Peer
ACS is programmed via the ACS Capability Structure in the NT function’s configuration space.
– The NT function supports ACS checks when the port operates in the following port operating
modes:
• Upstream switch port with NT function
• Upstream switch port with NT and DMA function
– In these modes, the ACS Capability Structure is linked into the NT function’s configuration space
(refer to section NT Function Capability Structures on page 19-22).
– The NT function does not support ACS checks when the port operates in any other mode.
The NT function applies the above ACS checks for TLPs it emits (i.e., TLPs received on another parti-
tion that have undergone NT address translation).
– ACS checks are not applied to completion TLPs generated by the NT function in response to a
received requests that target BAR 0 of the NT function, when this BAR is configured to map into
the NT function’s configuration space.
– ACS checks are not applied to punch-through configuration requests issued by the NT function.
Table 14.2 lists ACS checking and handling performed by the NT function. Note that none of the ACS
checks result in an ACS violation error.
1.
The PES32NT24xG2 does not support ACS Peer-to-Peer Egress Control among the functions of a multi-func-
tion upstream port.
2.
In a multi-function upstream port, ‘peer-to-peer’ implies traffic exchanged among the port functions (e.g., from
the port’s NT function to the port’s PCI-to-PCI bridge function).