41
PCI-X Layout Guidelines
PCI-X Layout Guidelines
6
This chapter describes several factors to be considered with a PCI/PCI-X design. These include the
PCI IDSEL, PCI RCOMP, PCI Interrupts, and PCI arbitration.
6.1
Interrupt Routing and IDSEL Lines
shows the 80331 connected to three PCI connectors. Notice that the interrupts are rotated
for each connector. The practice of Rotating INTs can also be used when connecting to individual
multifunction PCI devices as well. The IDSEL lines acts as chip selects during the configuration
cycles. Configuration cycles allow read and write access to one of the device configuration space
registers. The IDSEL lines can be mapped to upper address lines which are unused during the
configuration cycles. The ATU is hardwired to AD30 for IDSEL. Note that AD16 typically is
reserved for a PCI/PCI-X bridge. Each IDSEL line needs a 200 ohm series resistor on it as shown
in the figure below.
Figure 14.
Interrupt and IDSEL Mapping
INTA#
INTB#
INTC#
INTD#
IDSEL
PCI Connector 1
S_INT[D:A]#
S_AD[31:0]
AD20
PCI Connector 2
PCI Connector 3
Note: PCI Bus Interrupt Signals “Rotate” on Subsequent PCI Connectors.
INTA#
INTB#
INTC#
INTD#
INTA#
INTB#
INTC#
INTD#
IDSEL
AD17
INTB#
INTC#
INTD#
INTA#
INTA#
INTB#
INTC#
INTD#
IDSEL
AD18
INTC#
INTD#
INTA#
INTB#
Intel
®
80331 I/O
Processor
200
Ω
200
Ω
200
Ω
Summary of Contents for 80331
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Page 122: ...122 Intel 80331 I O Processor Design Guide Memory Controller ...
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