Intel
®
81341 and 81342—Introduction
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
50
Order Number: 315037-002US
1.5.3
Internal Busses
The 81341 and 81342 is architected around two internal busses: north internal bus and
south internal bus. The two busses use the same bus protocol. The north internal bus is
128-bit wide and operates at speed up to 400 MHz. The north internal bus connects the
two Intel XScale
®
processors, which have direct access to the DDR SDRAM. The north
internal bus is designed to provide the two Intel XScale
®
processors with low latency
access.
The south internal bus is 128-bits wide and operates at speeds up to 400 MHz. The
south internal bus provides data paths for large DMA generated burst transactions.
Both the internal address and data busses on the south internal bus are parity
protected on a byte-wise basis. The point-to-point interfaces between the agents
connected to the DDR SDRAM Memory Controllers are also parity protected on a byte-
wise basis.
1.5.4
Application DMA Controller
There are three Application DMA Channels. The Application DMA controller is dual-
ported - with one of its ports connected to the south internal bus and the other port to
the DDR SDRAM Memory controller. This Application DMA Controller allows low-latency,
high-throughput data transfers between PCI bus agents and the DDR memory. The
DMA controller also allows data transfer between DDR Memory. The DMA Controller
supports chaining and unaligned data transfers. It is programmable through the Intel
XScale
®
processor and the host processor.
Each Application DMA channel can also be programmed to operate as an XOR Engine
that provides low-latency, high-throughput data transfer capability between the ADMA
unit, the local DDR memory and the Primary PCI bus. It executes data transfers from
and to the local DDR memory, from the Primary PCI bus to the local DDR memory, or
from the local DDR memory to the Primary PCI bus. The XOR unit performs XOR
operations, computes parity, generates and verifies an eight byte Data Integrity field
which includes a 16- /32- bit Data Guard, performs memory block fills, and provides
the necessary programming interface.
The Intel XScale
®
processor supports L2 cache hardware coherency. Software can take
advantage of the hardware coherency support by placing the ADMA descriptors in
coherent memory space. The ADMA provides a control bit to enable this feature, and
software must also set up the coherent memory regions by programming the
appropriate page table entries. Refer to the “Memory Management” Chapter of the Intel
XScale
®
processor Specification for more details.
1.5.5
Address Translation Unit
The Address Translation Unit (ATU) allows PCI transactions direct access to the local
DDR SDRAM memory. The ATU provides the interface for the RAID Controller PCI
function. The ATU supports transactions between PCI address space and the internal
address space. Address translation is controlled through programmable registers
accessible from both the PCI interface and the Intel XScale
®
processor. Dual access to
registers allows flexibility in mapping the two address spaces. The ATU also supports
the extended capability configuration headers.