8. Interrupt Handling > Interrupt Sources
64
PEB383 User Manual
July 25, 2011
Integrated Device Technology, Inc.
Confidential - NDA Required
The Interrupt Message Generation module connects to the PCI Target Interface, external
PCI_INT[D:A]n interrupts, and the upstream posted buffer (see
). Assertion and de-assertion
of interrupts are stored in the form of Assert_INTx and Deassert_INTx flags. These flags are kept
asserted until the posted buffer can handle corresponding assert and de-assert messages. If an interrupt
pin is toggled when the PCI Interface is engaged with a PCI-initiated posted transaction, assert or
de-assert message loading into the upstream posted request buffer is stalled until the upstream posted
transaction terminates. Posted transactions are retried on the AD bus while an interrupt message is
loaded into the posted buffer. A De-assert message always follows an Assert message. More then one
interrupt pin can toggle at any point of time; however, a round-robin arbitration schedules the interrupt
message transmission.
There is no buffering for interrupt messages before loading them into the upstream posted buffer.
Therefore, only one pair of Assert_INTx and Deassert_INTx messages is loaded into the buffer when
allowed. In the worst case, the bridge may send duplicate messages; however, this is permitted
according to the
PCI Express Base Specification (Revision 1.1)
.
8.2
Interrupt Sources
The PEB383 does not have an internal source of interrupts: it forwards legacy PCI_INT[D:A]n
interrupts from the PCI Interface to the PCIe Interface in the form of Assert[D:A] and De-assert[D:A]
messages with PEB383 PCIe transaction IDs.
8.3
Interrupt Routing
Interrupt remapping is not performed by the PEB383. Legacy interrupts, PCI_INT[A:D]n, are routed to
the upstream PCIe port in the form of Assert_INTx and Deassert_INTx [A,B,C,D] messages.