Datasheet 201
Functional Description
5.17.2 Interrupt Mapping
Mapping Option #1 (Legacy Replacement Option)
In this case, the Legacy Replacement Rout bit (LEG_RT_CNF) is set. This forces the
mapping found in Table 5-42.
NOTE: The Legacy Option does not preclude delivery of IRQ0/IRQ8 using direct FSB interrupt
messages.
Mapping Option #2 (Standard Option)
In this case, the Legacy Replacement Rout bit (LEG_RT_CNF) is 0. Each timer has its
own routing control. The interrupts can be routed to various interrupts in the 8259 or
I/O APIC. A capabilities field indicates which interrupts are valid options for routing. If a
timer is set for edge-triggered mode, the timers should not be share with any PCI
interrupts.
For the PCH, the only supported interrupt values are as follows:
Timer 0 and 1: IRQ20, 21, 22 & 23 (I/O APIC only).
Timer 2: IRQ11 (8259 or I/O APIC) and IRQ20, 21, 22 & 23 (I/O APIC only).
Timer 3: IRQ12 (8259 or I/O APIC) and IRQ 20, 21, 22 & 23 (I/O APIC only).
Interrupts from Timer 4, 5, 6, 7 can only be delivered using direct FSB interrupt
messages.
5.17.3 Periodic vs. Non-Periodic Modes
Non-Periodic Mode
Timer 0 is configurable to 32 (default) or 64-bit mode, whereas Timers 1, 2 and 3 only
support 32-bit mode (See Section 20.1.5).
All of the timers support non-periodic mode.
Refer to Section 2.3.9.2.1 of the IA-PC HPET Specification for a description of this
mode.
Table 5-42. Legacy Replacement Routing
Timer 8259 Mapping APIC Mapping Comment
0IRQ0 IRQ2
In this case, the 8254 timer will
not cause any interrupts
1IRQ8 IRQ8
In this case, the RTC will not cause
any interrupts.
2 & 3
Per IRQ Routing
Field.
Per IRQ Routing Field
4, 5, 6, 7 not available not available
To Next Page
Loading...
Need help?
General
