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PXA250 and PXA210 Applications Processors Design Guide A-5
SA-1110/Applications Processor Migration
You can program GPIO pins to generate various clocks in both the SA-1110 and the PXA250
applications processors. For example, these are often used in audio codec designs to generate
clocks. The inter-relationships of some of these clocks have changed from the SA-1110 to the
PXA250 applications processor. You may need to select different GPIO pins and program different
configuration registers to provide similar functionality.
A.1.6 UCB1300
The SA-1110 supports a unique serial protocol for communication with the Philip’s UCB product
family: UCB1100, 1200 and 1300. This serial interface is not available on the PXA250
applications processor. Instead the PXA250 applications processor supports several industry
standard Audio codec Interfaces. You may also use I
2
S/I
2
C combinations and an AC’97 interface.
If an SA-1110 design utilizes this UCB interface then an alternative choice of components is
necessary for the PXA250 applications processor.
A.2 SA-1110 to PXA250 Software Migration Issues
The difficulty of migrating software from the SA-1110 to the PXA250 applications processor
depends on the amount of hardware and software interaction. SA-1110 applications running under
an Operating System, which use device driver interfaces, should move seamlessly between the two
devices.
There is one exception; any application that explicitly uses the Read Buffer to prefetch external
memory data into the SA-1110. This buffer does not exist on the PXA250 applications processor
and register #9 in Coprocessor #15 that was used to access it are not compatible to software.
As the Read Buffer prefetching activity was deemed to be a hint rather than an instruction,
applications can simply delete all references to the Read Buffer and still function correctly. They
may not even suffer a performance penalty, as the PXA250 ’hit-under-miss’ cache feature can turn
the entire data space into a prefetchable region without any explicit software direction.
Alternately, as a patch for software that cannot be modified, all applications must be limited to
User Mode execution, whereupon an Exception can be generated for all Coprocessor activity.
Such an exception manager needs to filter out the Read Buffer coprocessor calls, or convert them to
PXA250 PLD instructions that can preload a data cache value.
There are major software difference within the device initialization/configuration software and
device drivers, such as low-level code that controls the hardware.
The PXA250 applications processor has enhanced functionality and extra instructions not found in
the SA-1110. The PXA250 applications processor software is not backward compatibility to the
SA-1110. Once code is compiled for the PXA250 applications processor it is unlikely to run on the
SA-1110.