82801DB datasheet(32/587 Pages) INTEL

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Intel® 82801DB ICH4 Datasheet

Introduction

Compatibility Modules (DMA Controller, Timer/Counters, Interrupt

Controller)

The DMA controller incorporates the logic of two 82C37 DMA controllers, with seven

independently programmable channels. Channels 0–3 are hardwired to 8-bit, count-by-byte

transfers, and channels 5–7 are hardwired to 16-bit, count-by-word transfers. Any two of the seven

DMA channels can be programmed to support fast Type-F transfers.

The ICH4 supports two types of DMA (LPC and PC/PCI). DMA via LPC is similar to ISA DMA.

LPC DMA and PC/PCI DMA use the ICH4’s DMA controller. The PC/PCI protocol allows

PCI-based peripherals to initiate DMA cycles by encoding requests and grants via two PC/PCI

REQ#/GNT# pairs.

LPC DMA is handled through the use of the LDRQ# lines from peripherals and special encodings

on LAD[3:0] from the host. Single, Demand, Verify, and Increment modes are supported on the

LPC interface. Channels 0–3 are 8-bit channels. Channels 5–7 are 16-bit channels. Channel 4 is

reserved as a generic bus master request.

The timer/counter block contains three counters that are equivalent in function to those found in

one 82C54 programmable interval timer. These three counters are combined to provide the system

timer function, and speaker tone. The 14.31818 MHz oscillator input provides the clock source for

these three counters.

The ICH4 provides an ISA-Compatible Programmable Interrupt Controller (PIC) that incorporates

the functionality of two 82C59 interrupt controllers. The two interrupt controllers are cascaded so

that 14 external and two internal interrupts are possible. In addition, the ICH4 supports a serial

interrupt scheme.

All of the registers in these modules can be read and restored. This is required to save and restore

system state after power has been removed and restored to the platform.

Advanced Programmable Interrupt Controller (APIC)

In addition to the standard ISA compatible Programmable Interrupt Controller (PIC) described in

the previous section, the ICH4 incorporates the Advanced Programmable Interrupt Controller

(APIC).

Universal Serial Bus (USB) Controller

The ICH4 contains an Enhanced Host Controller Interface (EHCI) compliant host controller that

supports USB high-speed signaling. High-speed USB 2.0 allows data transfers up to 480 Mb/s

which is 40 times faster than full-speed USB. The ICH4 also contains three Universal Host

Controller Interface (UHCI) controllers that support USB full-speed and low-speed signaling.

The ICH4 supports 6 USB 2.0 ports. All six ports are high-speed, full-speed, and low-speed

capable. ICH4’s port-routing logic determines whether a USB port is controlled by one of the

UHCI controllers or by the EHCI controller. See Section 5.16, “USB UHCI Controllers (D29:F0,

F1 and F2) and Section 5.17, “USB EHCI Controller (D29:F7) for details.

82801DB Datasheet(PDF) 32 Page - Intel Corporation