NH82801HBM S LB9A Intel, NH82801HBM S LB9A Datasheet - Page 144

• Manufacturer Part Number: NH82801HBM S LB9A
• Description: CONTROLLER HUB, ICH8M, I/O, 82801HBM
• Manufacturer: Intel

Specifications of NH82801HBM S LB9A

• Power Dissipation Pd: 2.4W
• Digital Ic Case Style: BGA
• No. Of Pins: 676
• Pci Bus Type: I/O Controller Hub
• Pci Express Base Spec: PCIe 1.1
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

5.8.4.5
5.8.4.6
5.8.4.7
5.8.4.8
5.8.4.9
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Poll Mode
Poll mode can be used to conserve space in the interrupt vector table. Multiple
interrupts that can be serviced by one interrupt service routine do not need separate
vectors if the service routine uses the poll command. Poll mode can also be used to
expand the number of interrupts. The polling interrupt service routine can call the
appropriate service routine, instead of providing the interrupt vectors in the vector
table. In this mode, the INTR output is not used and the microprocessor internal
Interrupt Enable flip-flop is reset, disabling its interrupt input. Service to devices is
achieved by software using a Poll command.
The Poll command is issued by setting P=1 in OCW3. The PIC treats its next I/O read as
an interrupt acknowledge, sets the appropriate ISR bit if there is a request, and reads
the priority level. Interrupts are frozen from the OCW3 write to the I/O read. The byte
returned during the I/O read contains a 1 in bit 7 if there is an interrupt, and the binary
code of the highest priority level in bits 2:0.
Cascade Mode
The PIC in the ICH8 has one master 8259 and one slave 8259 cascaded onto the
master through IRQ2. This configuration can handle up to 15 separate priority levels.
The master controls the slaves through a three bit internal bus. In the ICH8, when the
master drives 010b on this bus, the slave controller takes responsibility for returning
the interrupt vector. An EOI command must be issued twice: once for the master and
once for the slave.
Edge and Level Triggered Mode
In ISA systems this mode is programmed using bit 3 in ICW1, which sets level or edge
for the entire controller. In the ICH8, this bit is disabled and a new register for edge and
level triggered mode selection, per interrupt input, is included. This is the Edge/Level
control Registers ELCR1 and ELCR2.
If an ELCR bit is 0, an interrupt request will be recognized by a low-to-high transition
on the corresponding IRQ input. The IRQ input can remain high without generating
another interrupt. If an ELCR bit is 1, an interrupt request will be recognized by a high
level on the corresponding IRQ input and there is no need for an edge detection. The
interrupt request must be removed before the EOI command is issued to prevent a
second interrupt from occurring.
In both the edge and level triggered modes, the IRQ inputs must remain active until
after the falling edge of the first internal INTA#. If the IRQ input goes inactive before
this time, a default IRQ7 vector is returned.
End of Interrupt (EOI) Operations
An EOI can occur in one of two fashions: by a command word write issued to the PIC
before returning from a service routine, the EOI command; or automatically when AEOI
bit in ICW4 is set to 1.
Normal End of Interrupt
In normal EOI, software writes an EOI command before leaving the interrupt service
routine to mark the interrupt as completed. There are two forms of EOI commands:
Specific and Non-Specific. When a Non-Specific EOI command is issued, the PIC clears
the highest ISR bit of those that are set to 1. Non-Specific EOI is the normal mode of
operation of the PIC within the ICH8, as the interrupt being serviced currently is the
interrupt entered with the interrupt acknowledge. When the PIC is operated in modes
that preserve the fully nested structure, software can determine which ISR bit to clear
Intel
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Functional Description
ICH8 Family Datasheet