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Memory Switch
Copyright © 12/13/06 Marvell
CONFIDENTIAL
Doc. No. MV-TBD-00 Rev. A
December 13, 2006
Document Classification: Proprietary Information
Page 61
Not approved by Document Control. For review only.
Memory Switch
3
3.1
Overview
This chapter documents the PXA300 processor or PXA310 processor internal switch bus (memory switch) that
provides a dedicated connection to/from the initiators (core subsystem, system bus #1, and system bus #2) to the
completers (external static-memory controller, external dynamic-memory controller, internal SRAM memory
controller, system bus #1, and system bus #2) for the data transfers. The term agent is used to refer to either
initiators or completers.
By duplicating the data paths within the processor, the memory switch allows for very high internal data
bandwidth between various controllers. The memory switch also allows for lower latencies due to fewer
controllers competing for a single bus.
This chapter refers to agents that can initiate new read or write transfers as initiators. Similarly, the agents that
complete those transfers are referred to as completers. The completer interface and initiator interface are the
logic that connects the completer or initiator to the memory switch bus. See
for a graphic
representation of the memory switch bus, which separates the completer from the completer interface and the
initiator from the initiator interface.
The core subsystem is comprised of the Intel XScale
®
microarchitecture (core), the Wireless MMX
TM
2
coprocessor , and the internal cache. These subsystem components are referred to as though they were a single
unit in most cases to simplify the concepts being described. When necessary, the separate components are
referred to individually for greater detail.
3.1.1
Differences Between PXA300 Processor and PXA310
Processor
There are no differences between the memory switch controllers of PXA300 processor and the PXA310
processor.
3.2
Features
•
All the bus clients are connected in a crossbar structure to maximize bandwidth and minimize latency
•
32-bit address, 64-bit write data, 64-bit read data per agent
•
Supports three initiators (core subsystem, system bus #1, and system bus #2) and six completers (external
static-memory controller, external dynamic-memory controller, internal SRAM memory controller, internal
flash-memory controller, system bus #1, and system bus #2)
•
Allows concurrent accesses to all completers from any initiator
•
Programmable priority mechanism in each completer
•
Supports atomic operations from the Intel XScale
®
microarchitecture