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10 Interrupt Configurations
The PCIXX20 controller provides system designers with great flexibility in configuring interrupts.
The PCIXX20 controller allows three interrupt modes which are selected via bits 2:1 of the
device control register at PCI configuration offset 92h.
PCI interrupts are available on INTA . This signal is available on MFUNC0. The multifunction
routing register at PCI configuration offset 8Ch must be programmed correspondingly. PCI
interrupts can also be signaled through IRQSER.
Windows XP has simplified the interrupt routing by allowing many 16-bit cards which used ISA
IRQs in previous OSs to use PCI interrupts. More information on interrupts in Windows XP can
be found at:
http://www.microsoft.com/hwdev/bus/cardbus/PCMCIA-IRQrouting.asp
10.1 Parallel PCI Interrupts Only
The parallel PCI interrupts only mode is selected by programming bits 2:1 to a value of 00b.
This allows interrupts to be routed through INTA . This is not a recommended interrupt
configuration because some 16-bit PC Cards require legacy ISA interrupts and do not function
properly.
When using one of the parallel PCI interrupt modes, INTA , INTB , INTC , and INTD must be
connected to the PCI interrupt lines. If the INTRTIE bit (system control register, PCI offset 80h,
bit 29) is set, then both functions signal and report INTA , therefore, only INTA needs to be
routed. The TIEALL bit (system control register, PCI offset 80h, bit 28) ties INTA , INTB , INTC ,
and INTD together internally. The INTRTIE and TIEALL bits affect the read-only value provided
through accesses to the interrupt pin register (PCI offset 3Dh, see Section 4.24). Table 12
summarizes the interrupt signaling modes.
INTIE
TIEALL
Bit
Bit
0
0
1
0
X
1
10.2 Serial IRQ and Parallel PCI Interrupts
The serial IRQ and parallel PCI interrupts mode is selected by programming bits 2:1 to a value
of 10b. This allows interrupts to be routed through IRQSER and INTA . This is the
recommended interrupt configuration for a PCI add-in card implementation of the PCIXX20
controller. INTA can be routed through the PCI edge connector while IRQSER must be
attached to a serial IRQ input on the motherboard. If no serial IRQ input is available, then this
mode still allows CardBus cards to function properly. However, some 16-bit cards may not.
Table 12.
Interrupt Pin Register Cross Reference
INTPIN
INTPIN
Function 0
Function 1
CardBus
CardBus
01h INTA
02h INTB
01h INTA
01h INTA
01h INTA
01h INTA
PCI7620/PCI7420/PCI6620/PCI6420 Implementation Guide
INTPIN
Function 2
1394 OHCI
Determined by bits 6-5 (INT_SEL_FIELD)
03h INTC
in flash media general control register
(PCI offset 0x86h)
03h INTC
01h INTA
01h INTA
INTPIN
Function 3
Flash Media
SCPU019
35
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