VMIC VMICPCI-7755, Product Manual

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VMICPCI-7755 Product Manual
PCI Interrupts
Interrupts on Peripheral Component Interconnect (PCI) Local Bus are optional and
defined as “level sensitive,” asserted low (negative true), using open drain output
drivers. The assertion and de-assertion of an interrupt line, INTx#, is asynchronous to
CLK. A device asserts its INTx# line when requesting attention from its device driver.
Once the INTx# signal is asserted, it remains asserted until the device driver clears the
pending request. When the request is cleared, the device de-asserts its INTx# signal.
PCI defines one interrupt line for a single function device and up to four interrupt
lines for a multifunction device or connector. For a single function device, only INTA#
may be used while the other three interrupt lines have no meaning. Figure 2-1 on
page 46 depicts the VMICPCI-7755 interrupt logic pertaining to CompactPCI
operations and the PMC site.
Any function on a multifunction device can be connected to any of the INTx# lines.
The Interrupt Pin register defines which INTx# line the function uses to request an
interrupt. If a device implements a single INTx# line, it is called INTA#; if it
implements two lines, they are called INTA# and INTB#; and so forth. For a
multifunction device, all functions may use the same INTx# line, or each may have its
own (up to a maximum of four functions), or any combination thereof. A single
function can never generate an interrupt request on more than one INTx# line.
The slave PIC accepts the CompactPCI interrupts through lines that are defined by the
BIOS. The BIOS defines which interrupt line to utilize depending on which system
requires the use of the line.
67-6F 103-111 Reserved by DOS Same as Real Mode
70 112 IRQ8 Real Time Clock
71 113 IRQ9 Redirect to IRQ2
72 114 IRQ10 Not Assigned
73 115 IRQ11 Not Assigned
74 116 IRQ12 Mouse
75 117 IRQ13 Math Coprocessor
76 118 IRQ14 AT Hard Drive
77 119 IRQ15 Flash Drive
78-7F 120-127 Reserved by DOS Same as Real Mode
80-F0 128-240 Reserved for BASIC Same as Real Mode
F1-FF 241-255 Reserved by DOS Same as Real Mode
Table 2-3 PC Interrupt Vector Table (Continued)
INTERRUPT NO.
IRQ
LINE
REAL MODE PROTECTED MODE
HEX DEC