AN2113 Freescale Semiconductor / Motorola, AN2113 Datasheet - Page 10

• Manufacturer Part Number: AN2113
• Description: AN2113 Multichannel Voice Coding System on the RTXC Operating System
• Manufacturer: Freescale Semiconductor / Motorola

System Overview
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6.1 Target Hardware
By selecting the tasks properly, the developer can isolate the “application” tasks (labeled Task 1 through
Task n) from the “device-specific” tasks (shown as interrupt service routines and device driver tasks),
which makes it easier to reuse or migrate the application tasks across processors or applications. The
RTXC API provides access to the following services and objects:
Though there is no defined way to design an application with an RTOS, there are general guidelines. Start
by breaking the application into tasks by drawing data flow diagrams and determining the input,
processing function, and output for each task. Define which events and conditions require a task to
perform their function. Initially assign priorities based on how often each task must perform its function:
the highest priority goes to the most time-critical task.
In its distribution form, RTXC is not executable. RTXC is furnished as a set of C and assembly language
source files. You must first compile RTXC source code and then link it with the object files of the
application programs and other system configuration files. Developers should treat RTXC as any other
software library. It is not necessary to know how RTXC functions internally. You need only know what
functionality RTXC provides and what RTXC kernel services achieve the desired result. Knowledge of
which inputs produce which outputs is all that is needed. Additionally, not all RTXC objects are needed in
an application. In fact, an effective application can be implemented using tasks and semaphores alone.
Therefore, RTXC allows scaling of its software to include only the modules and API calls that the
application developer wishes to use, thus improving memory and execution efficiency.
The system discussed here executes multiple channels of the IS-96-A voice coder on a Motorola
DSP56307EVM. This section outlines the target hardware and application software developed for this
project.
The target hardware is a DSP56307EVM with a connection to a daughter board that contains four Crystal
CS4215 stereo audio codecs. All software described in this application note runs on the DSP56307EVM.
This board can be purchased for development purposes. The EVM has an on-board DSP56307 and audio
codec. You can therefore program the DSP to process voice coming from an audio source through the A/D
converter and then send the processed data back out through the D/A converter to hear through
headphones or speakers. The EVM also has on-board SRAM and Flash memory.
The DSP56307 is a powerful device that can process multiple channels of voice data. The audio codec on
the DSP56307EVM allows processing for two channels of data. To demonstrate the processing
capabilities of the DSP56307, more than one audio codec is required. We developed the multichannel
board primarily to demonstrate the execution of multiple voice coding channels on a DSP56307EVM. The
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System Overview
Task management: starting and stopping tasks, and so on.
Event management: semaphores.
Inter-task communication: mailboxes, messages, and queues.
Resource management: sharing system resources.
Time management: timers.
Memory management: memory partitions.
Freescale Semiconductor, Inc.
For More Information On This Product,
Multichannel Voice Coding System
Go to: www.freescale.com