Technical information

2 Porting and Optimizing DSP56800 Applications to DSP56800E 

1.1 Case Study

The application chosen as an example to be ported was the implementation of the International

Telecommunications Union (ITU) Recommendation V.22 bis. The original code was taken from Freescale

Embedded Software Development Kit (SDK) version 2.1. This software development kit, which runs with

Metrowerks CodeWarrior 3.5.1 for the DSP56800 Family, can be found at the following URL:

http://www.freescale.com

The initial application could be run in two modes: either using a digital or an analog loopback (the latter

could be run only on DSP56824 EVM). Modifications were made to the original code to run it only on the

simulator (using only a digital loopback). Also, all calls to the SDK libraries were eliminated. These

modifications affected only the tester, not the modem library.

The original code was initially optimized for the DSP56800. The result was considered the reference code

for the next round of optimization (employing only the new features introduced by DSP56800E). The

performance improvement gained after DSP56800E optimization is measured against the performance of

this reference code and is discussed in Section 3, “Optimizing the Ported Code.”

1.2 References and Tools

This application note refers to the DSP56800E 16-Bit Digital Signal Processor Core Reference Manual

(Order number DSP56800ERM/D) as the Core Reference Manual.

The tools used for developing and testing the code discussed in this document were the following:

• Metrowerks CodeWarrior 3.5.1 for DSP56800

• Prototype tools for DSP56800E including the assembler and the simulator

The porting process requires knowledge of several DSP56800 topics that are not explained in this

application note. The following documents provide necessary information on these topics:

• DSP56800 16-Bit Digital Signal Processor Family Manual (Rev. 1.00, order number

DSP56800FM/D)

• Freescale Embedded SDK 2.1 Help and Documentation: information about SDK libraries and

system calls

In addition, coding requirements and recommendations used in this application note derive from a

forthcoming guide on porting applications from the DSP56800 platform to the DSP56800E platform.

2 Application Porting

This section investigates porting a DSP56800 application to the DSP56800E architecture.

The entire application was tested and developed using a 16-bit address model for program and data

memory space. Although the DSP56800E has larger addressing capabilities, they are not necessary for this

application. Problems can result from using the extended DSP56800E program and data memory space for

DSP56800 code. Section 6, “Converting Applications for Increased Data and Program Memory,” details

these problems.

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