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Chapter 4 System Support
4.4SYSTEM RESOURCES
This section describes the availability and basic control of major subsystems, otherwise known as resource allocation or simply “system resources.” System resources are provided on a priority basis through hardware interrupts and DMA requests and grants.
4.4.1 INTERRUPTS
The microprocessor uses two types of hardware interrupts; maskable and nonmaskable. A maskable interrupt can be enabled or disabled within the microprocessor by the use of the STI and CLI instructions. A nonmaskable interrupt cannot be masked off within the microprocessor, although it may be inhibited by hardware or software means external to the microprocessor.
4.4.1.1Maskable Interrupts
The maskable interrupt is a
Figure 4-9 shows the routing of PCI and ISA interrupts. Most IRQs are routed through the I/O controller, which contains a serializing function. A serialized interrupt stream is applied to the MCP component.
I/O & SM Functions
IRQ3..7, 9..12, 14,15
LPC47B367
I/O Cntlr.
Interrupt
Serializer
Serial IRQ
MCP
IDE IRQ14,15 Hard Drives
Interrupt
INTR-
Processor |
PCI Peripherals
INTA-..H-
Processing
APIC bus |
Figure 4-10. Maskable Interrupt Processing, Block Diagram
Interrupts may be processed in one of two modes (selectable through the F10 Setup utility):
♦8259 mode
♦APIC mode
Second Edition – April 2003