Interrupt Controller Registers - Intel 460GX Software Developer’s Manual

LPC/FWH Interface Configuration
Bit
7:0
11.2.1.11 Dmc–Dma Master Clear Register (I/O)
I/O Address:
Default Value:
Attribute:
This software instruction has the same effect as the hardware Reset.
Bit
7:0
11.2.1.12 Dclm–Dma Clear Mask Register (I/O)
I/O Address:
Default Value:
Attribute:
This command clears the mask bits of all four channels, enabling them to accept DMA requests.
Bit
7:0
11.2.2

Interrupt Controller Registers

The IFB contains an interrupt controller that incorporates the Functionality of two 82C59 interrupt
controllers. The interrupt registers control the operation of the interrupt controller.
11.2.2.1 Icw1–Initialization Command Word 1 Register (I/O)
I/O Address:
Default Value:
Attribute:
A write to Initialization Command Word 1 starts the interrupt controller initialization sequence.
Addresses 020h and 0A0h are referred to as the base addresses of CNTRL-1 and CNTRL-2,
respectively. An I/O write to the CNTRL-1 or CNTRL-2 base address with bit 4 equal to 1 is
interpreted as ICW1. For IFB-based systems, three I/O writes to "base address + 1" must follow the
ICW1. The first write to "base address + 1" performs ICW2, the second write performs ICW3, and
the third write performs ICW4.
ICW1 starts the initialization sequence during which the following automatically occur:
1. The Interrupt Mask register is cleared.
2. IRQ7 input is assigned priority 7.
3. The slave mode address is set to 7.
4. Special Mask Mode is cleared and Status Read is set to IRR.
11-20
Clear Byte Pointer. No specific pattern. Command enabled with a write to the I/O port
address.
Channel 0-3–00Dh; Channel 4-7–0DAh
All bits undefined
Write Only
Master Clear. No specific pattern. Command enabled with a write to the I/O port address
Channel 0-3–00Eh; Channel 4-7–0DCh
All bits undefined
Write Only
Clear Mask Register. No specific pattern. Command enabled with a write to the I/O port
address.
INT CNTRL-1–020h; INT CNTRL-2–0A0h
All bits undefined
Write Only
Description
Description
Description
Intel® 460GX Chipset Software Developer's Manual