Intel PXA250 and PXA210 manual A.2 SA-1110 to PXA250 Software Migration Issues, A.1.6 UCB1300

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 I2S/I2C 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.

PXA250 and PXA210 Applications Processors Design Guide A-5