Intel
82801BA ICH2 Datasheet
5-5
Functional Description
Type 1 to Type 0 Conversion
When the bus number for the Type 1 configuration cycle matches the PCI (Secondary) bus number,
the ICH2 converts the address as follows:
For device numbers 0 through 15, only one bit of the PCI address [31:16] is set. If the device
number is 0, AD[16] is set; if the device number is 1, AD[17] is set; etc.
The ICH2 always drives 0s on bits AD[15:11] when converting Type 1 configurations cycles
to Type 0 configuration cycles on PCI.
Address bits [10:1] are also passed unchanged to PCI.
Address bit [0] is changed to 0.
5.1.7
PCI Dual Address Cycle (DAC) Support
The ICH2 supports Dual Address Cycle (DAC) format on PCI for cycles from PCI initiators to
main memory. This allows PCI masters to generate an address up to 44 bits. The size of the actual
supported memory space will be determined by the memory controller and the processor.
The DAC mode is only supported for PCI adapters and is not supported for any of the internal PCI
masters (IDE, LAN, USB, AC’97, 8237 DMA, etc.). ICH2 does not support DAC for processor-
initiated cycles.
When a PCI master wants to initiate a cycle with an address above 4 GB, it follows the following
behavioral rules (See PCI 2.2 Specification, section 3.9 for more details):
1. On the first clock of the cycle (when FRAME# is first active), the peripheral uses the DAC
encoding on the C/BE# signals. This unique encoding is 1101.
2. Also during the first clock, the peripheral drives the AD[31:0] signals with the low address.
3. On the second clock, the peripheral drives AD[31:0] with the high address. The address is
right justified: A[43:32] appear on AD[12:0]. The value of AD[31:13] is expected to be 0,
however the ICH2 will ignore these bits. C/BE# indicate the bus command type (Memory
Read, Memory Write, etc.)
4. The rest of the cycle proceeds normally.
5.2
LAN Controller (B1:D8:F0)
The ICH2’s integrated LAN Controller includes a 32-bit PCI controller that provides enhanced
scatter-gather bus mastering capabilities and enables the LAN Controller to perform high speed
data transfers over the PCI bus. Its bus master capabilities enable the component to process high
level commands and perform multiple operations, which lowers processor utilization by off-
loading communication tasks from the processor. Two large transmit and receive FIFOs of 3 KB
each help prevent data underruns and overruns while waiting for bus accesses. This enables the
integrated LAN Controller to transmit data with minimum interframe spacing (IFS).
The ICH2 integrated LAN Controller can operate in either full duplex or half duplex mode. In full
duplex mode the LAN Controller adheres with the IEEE 802.3x Flow Control specification. Half
duplex performance is enhanced by a proprietary collision reduction mechanism.
The integrated LAN Controller also includes an interface to a serial (4-pin) EEPROM. The
EEPROM provides power-on initialization for hardware and software configuration parameters.
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