Interphase Tech 4538 - Manual (Page 42)

The PCI Bridge
20 Interphase Corporation
Interrupt pins –INT1 to –INT4 are configured as output ports and conventionally associated
with doorbell bits DB3 to DB6 in the PowerSpan. Each doorbell bit, when set, will activate
its corresponding interrupt pin (level = 0), and when reset will deactivate it (level =1).
Interrupt pin –INT5 is used as an input. Its state can be read in the PowerSpan Interrupt
status register. As an interrupt source, it was decided not to map it to any interrupt output,
so it will not generate interrupts. As an interrupt output pin, it was decided not to associate
it to any interrupt source.
Interrupt pins –INTA and –INT0, used for true interrupt functions, have several other
interrupt sources, such as Mailboxes interrupts, DMA interrupts, I²O interrupts, PCI bus or
local bus error interrupts, etc. They are conventionally associated with a doorbell bit for
software activation capability.
PCI to Local Interrupt (ATN)
The PowerSpan Interrupt pin –INT0 is used to control the PCI-to-Local Interrupt (renamed
ATN (Attention) in the software examples).
Table 1-21. PowerSpan Interrupt Pin Usage
PowerSpan Pin Doorbell Dir Signal Name Usage
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