IDT 89HPES16NT2, User Manual

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IDT Non-Transparent Mode Operation
PES16NT2 User Manual 10 - 6 April 15, 2008
Notes Treating a transaction as an unsupported request means setting the appropriate status bits and, if
enabled, generating an error message. If the transaction was a non-posted, this also means generating a
completion with status UR. See the PCIe base specification for details.
The NTB merely translates fields in TLPs, it does not restructure TLPs. Therefore, 32-bit address routed
transactions must map to 32-bit address transactions on the other side of the NTB and 64-bit address
routed transactions must map to 64-bit address transactions on the other side of the NTB. The behavior of
the NTB when 32-bit address routed transactions are mapped to 64-bit addresses or 64-bit address routed
transactions are mapped to 32-bit addresses is undefined.
Non-Posted Address Routed Transactions
Non-posted address routed transactions are handled by the NTB endpoints in exactly the same manner
as posted address routed transactions except that there is a completion associated with the transaction that
needs to traverse the non-transparent bridge from the opposite side to the side on which the original initi-
ator is located.
Completion transactions are routed by ID (i.e., by bus, device, and function number). When a comple-
tion is generated, it is routed by ID back to the opposite side of the non-transparent bridge. This is because
the bus number in the request transaction corresponds to that of the NTB and the NTB opposite side
endpoint is the only device on that bus. When a completion is received by the opposite side NTB endpoint,
a mapping table entry address is formed using the device and function numbers of the requesters ID field in
the TLP. In the request transaction, these fields were initialized with a mapping table entry. Thus, in the
completion transaction, these fields should point to the mapping table entry containing the bus, device and
function numbers of the original requestor.
The mapping table entry address formed from the device and function numbers is used to index into the
mapping table corresponding to the opposite side of the NTB from which the completion was received. If
the mapping table entry is valid, then the completion is routed through the NTB. The bus, device and func-
tion numbers of the requester ID of the forwarded transaction are replaced with the corresponding values in
the associated mapping table entry. The completer ID of the forwarded transaction is replaced with the bus,
device and function numbers of the NTB endpoint on which the completion is emitted (i.e., the NTB
endpoint side opposite to that on which the completion was received).
If the mapping table entry is invalid, or if the mapping table entry address does not point to a valid entry,
then the transaction is treated as an unexpected completion and the Reverse Mapping Table Miss
(RMTMISS) bit is set in the NTBSTS register of the NTB endpoint on which the transaction was received.
A completion received by the internal endpoint that maps to the external domain when the Port C link is
down is treated as a mapping table miss. When this occurs, the transaction is treated as an unexpected
completion and the Reverse Mapping Table Miss (RMTMISS) bit is set in the internal endpoint NTBSTS
register.
ID Routing
Other than completion transactions described in section Address Routing on page 10-3, ID routing is not
supported through the non-transparent bridge and are discarded.
Route to Root Implicit Routing
Route to root implicit routing is not supported through the non-transparent bridge and are discarded.
Broadcast from Root Implicit Routing
Broadcast from root implicit routing is not supported through the non-transparent bridge and is
discarded.
Local Terminate at Receiver Implicit Routing
Local terminate at receiver implicit routed transactions terminate at the NTB endpoint at which they are
received and therefore are not forwarded through the non-transparent bridge.