JAJSQ97J may 2009 – january 2021 XIO2001
PRODUCTION DATA
When properly configured, the bridge converts PCI bus serial IRQ interrupts into PCI Express message signaled interrupts (MSI). classic PCI configuration register space is provided to enable this feature. The following list identifies the involved configuration registers:
A PCI Express MSI is generated based on the settings in the serial IRQ edge control register. If the system is configured for edge mode, then an MSI message is sent when the corresponding serial IRQ interface sample phase transitions from low to high. If the system is configured for level mode, then an MSI message is sent when the corresponding IRQ status bit in the serial IRQ status register changes from low to high.
The bridge has a dedicated SERIRQ terminal for all PCI bus devices that support serialized interrupts. This SERIRQ interface is synchronous to the PCI bus clock input (CLK) frequency. The bridge always generates a 17-phase serial IRQ stream. Internally, the bridge detects only 16 IRQ interrupts, IRQ0 frame through IRQ15 frame. The IOCHCK frame is not monitored by the serial IRQ state machine and never generates an IRQ interrupt or MSI message.
The multiple message enable (MM_EN) field determines the number of unique MSI messages that are sent upstream on the PCI Express link. From 1 message to 16 messages, in powers of 2, are selectable. If fewer than 16 messages are selected, then the mapping from IRQ interrupts to MSI messages is aliased. Table 9-1 illustrates the IRQ interrupt to MSI message mapping based on the number of enabling messages.
IRQ INTERRUPT | 1 MESSAGE ENABLED | 2 MESSAGES ENABLED | 4 MESSAGES ENABLED | 8 MESSAGES ENABLED | 16 MESSAGES ENABLED |
---|---|---|---|---|---|
IRQ0 | MSI MSG #0 | MSI MSG #0 | MSI MSG #0 | MSI MSG #0 | MSI MSG #0 |
IRQ1 | MSI MSG #0 | MSI MSG #1 | MSI MSG #1 | MSI MSG #1 | MSI MSG #1 |
IRQ2 | MSI MSG #0 | MSI MSG #0 | MSI MSG #2 | MSI MSG #2 | MSI MSG #2 |
IRQ3 | MSI MSG #0 | MSI MSG #1 | MSI MSG #3 | MSI MSG #3 | MSI MSG #3 |
IRQ4 | MSI MSG #0 | MSI MSG #0 | MSI MSG #0 | MSI MSG #4 | MSI MSG #4 |
IRQ5 | MSI MSG #0 | MSI MSG #1 | MSI MSG #1 | MSI MSG #5 | MSI MSG #5 |
IRQ6 | MSI MSG #0 | MSI MSG #0 | MSI MSG #2 | MSI MSG #6 | MSI MSG #6 |
IRQ7 | MSI MSG #0 | MSI MSG #1 | MSI MSG #3 | MSI MSG #7 | MSI MSG #7 |
IRQ8 | MSI MSG #0 | MSI MSG #0 | MSI MSG #0 | MSI MSG #0 | MSI MSG #8 |
IRQ9 | MSI MSG #0 | MSI MSG #1 | MSI MSG #1 | MSI MSG #1 | MSI MSG #9 |
IRQ10 | MSI MSG #0 | MSI MSG #0 | MSI MSG #2 | MSI MSG #2 | MSI MSG #10 |
IRQ11 | MSI MSG #0 | MSI MSG #1 | MSI MSG #3 | MSI MSG #3 | MSI MSG #11 |
IRQ12 | MSI MSG #0 | MSI MSG #0 | MSI MSG #0 | MSI MSG #4 | MSI MSG #12 |
IRQ13 | MSI MSG #0 | MSI MSG #1 | MSI MSG #1 | MSI MSG #5 | MSI MSG #13 |
IRQ14 | MSI MSG #0 | MSI MSG #0 | MSI MSG #2 | MSI MSG #6 | MSI MSG #14 |
IRQ15 | MSI MSG #0 | MSI MSG #1 | MSI MSG #3 | MSI MSG #7 | MSI MSG #15 |
The MSI message format is compatible with the PCI Express request header format for 32-bit and 64-bit memory write transactions. The system message and message number fields are included in bytes 0 and 1 of the data payload.