82801BA Datasheet, PDF (33/498 Pages) Intel Corporation – Intel 82801BA I/O Controller Hub 2 (ICH2) and Intel 82801BAM I/O Controller Hub 2 Mobile

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 ICH2 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 ICH2’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 ICH2 provides an ISA-Compatible interrupt controller 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 ICH2 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 circuit.
Advanced Programmable Interrupt Controller (APIC)
In addition to the standard ISA compatible interrupt controller (PIC) described in the previous
section, the ICH2 incorporates the Advanced Programmable Interrupt Controller (APIC). While
the standard interrupt controller is intended for use in a uni-processor system, APIC can be used in
either a uni-processor or multi-processor system.
Enhanced Universal Serial Bus (USB) Controller
The USB controller provides enhanced support for the Universal Host Controller Interface (UHCI).
This includes support that allows legacy software to use a USB-based keyboard and mouse. The
ICH2 is USB Revision 1.1 compliant. The ICH2 contains two USB Host Controllers. Each Host
Controller includes a root hub with two separate USB ports each, for a total of 4 USB ports. See
Section 5.16, “USB Controller (Device 31:Functions 2 and 4)” on page 5-108 for details.
82801BA ICH2 and 82801BAM ICH2-M Datasheet
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