User Guide

Intel® 41210 Serial to Parallel PCI Bridge Design Guide 31
PCI-X Layout Guidelines 8
This chapter describes several factors to be considered with a 41210 Bridge PCI/PCI-X design.
These include the PCI IDSEL, PCI RCOMP, PCI Interrupts and PCI arbitration.
8.1 Interrupts
PCI Express provides interrupt messages that emulate the legacy wired mechanism. This allows IO
devices to signal PCI-style interrupts using a pair of ASSERT and DEASSERT messages This
message pairing preserves the level-sensitive semantics of the PCI interrupts on PCI Express.
The 41210 Bridge uses four interrupts - A_INTA:A_INTD on bus A segment and four interrupts
B_INTA:B_INTD that corresponding to the four interrupts defined in the PCI specification. The
41210 Bridge routes its PCI interrupt pins and the internal interrupts, to PCI Express INTx
interrupts according to Table 4.
The 41210 Bridge will use its primary bus number and device number in the Requester ID field for
the PCI Express INTx messages. As stated in the PCI Express specification, the function number is
reserved for interrupt messages and will always be 0.
Table 4. INTx Routing Table
A_INT# Interrupt Pins B_INT# Interrupt Pins PCI Express INTx Message
A_INTA B_INTA INTA
A_INTB B_INTB INTB
A_INTC B_INTC INTC
A_INTD B_INTD INTD