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A-8 PXA250 and PXA210 Applications Processors Design Guide
SA-1110/Applications Processor Migration
A.3.1 Intel® XScale™ Microarchitecture
The PXA250 applications processor is a system on a chip that includes Intel’s new microprocessor
megacell. This includes Intel
® Superpipelined Technology and a new optimized cache
architecture that allows program execution to continue despite data cache misses.
The PXA250 applications processor supports:
• ARM* Architecture v5 instructions, including ARM’s Thumb extensions
• DSP Extensions but not ARM’s optional Vector Floating Point instructions
Appendix A in the Intel 80200 Developers’ manual, Order# 273411-002 [http://
developer.intel.com], is the best guide to the new capabilities available in the Intel® XScale™
Megacell's Instruction Set.
Using a software development toolset that takes specific advantage of Intel
® XScale™
microarchitecture, and Intel
® Media Processing Technology could give you substantial
performance benefits.
The PXA250 applications processor offers increased performance at similar clock rates, and also a
wider range of operating clock rates at lower voltages. The overall benefit is more work done for
less battery power.
A.3.2 Debugging
New PXA250 hardware creates new debugging possibilities. You can use the JTAG test port to
download programs into a dedicated memory area to act as a debug monitor. Applications can be
inspected and performance data, such as cache hit rates, can be measured via a dialog over JTAG.
These features offer developers far more visibility inside a PXA250 system improving time to
market.
A.3.3 Cache Attributes
The PXA250 applications processor has twice the instruction cache and four times the data cache
of the SA-1110. The Caches can be locked for optimized code or data and for reliability the caches
are now covered by parity protection.
To take advantage of cache locking software, data must be selected and specifically loaded and
locked into cache.
To take advantage of new features such as Write-Through mode for external IO buffers, page tables
will need to be revisited in boot software.
A.3.4 Other features
As mentioned before, the PXA250 DMA controller is highly versatile. With 16 channels it can be
utilized as:
• Several serial ports in parallel
• A general-purpose memory move capability
• A fast interface for external companion devices