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XIO2001: Six PCI devices but only four interrupt lines

cxg
Prodigy 20 points
Part Number: XIO2001

Hello,

I'm struggling to understand how the XIO2001 can handle interrupts from 6 different PCI devices if it only has 4 interrupt lines. I'm looking at Implementation Guide: Interrupt Configurations and honestly I'm not comprehending what it is suggesting. It talks about 16 device numbers and the Interrupt Binding on Option Cards, which I don't understand. Would multiplexing or something similar work here? I'm not very knowledgeable on the subject yet so if you could point me to the right direction on how figure this out would be great. If you could provide a design recommendation would also be very much appreciated.  

Thanks

  • 0
    TI__Mastermind 35130 points
    Hi Cristobal,

    You can reference section 3.2 of the EVM Guide: www.ti.com/.../scpu031b.pdf

    and also the PCI Local Bus Specification for more information: www.xilinx.com/.../PCI_SPEV_V3_0.pdf

    Regards,
    I.K.
  • 0 in reply to Ikechukwu Anyiam
    Prodigy 20 points

    Thanks, the PCI specifciation was very informative. That should teach me to read the related documents.  So single function devices can only use INTA, which all the 6 PCI devices that we are using are, but it's possible to route INTA from PCI device to the other 3 INTx pins. 

    If I'm understanding this correctly, only 4 single function devices that have INTA# can be used with the XIO2001. INTA# pin from device 0, 1, 2, and 3 can go to INTA, INTB, INTC, INTD of the XIO2001, respectively, but the rest of the devices have to be multi-function devices. Is this correct or is there a way the have 6 different single function devices?

    Thanks

  • 0 in reply to cxg
    Guru 317250 points
    A PCI bus has four interrupt lines. A bus can have up to sixteen devices, with four interrupt outputs each, so interrupt lines are shared.

    A device calls its own interrupt outputs "A"/"B"/"C"/"D", but for each device, these signals are routed to different inputs of the upstream bridge to reduce the probability that interrupts actually are shared. (The specific routing shown in the table above is required so that the host software is able to map interrupts to devices.)

    If there are more than four devices (with one interrupt each), some interrupts are shared. If there are two devices (with one interrupt each) at numbers 0 and 4, then they share the interrupt. And if some devices have more than one interrupt, more interrupts lines must be shared.