16.1 Core file: introduction to six-channel board for ti evm320c5

The six channel surround sound board

The six-channel board attaches to the top of the DSP evaluation module and replaces its onboard, one-channel A/Dand D/A with six channels of D/A and two channels of A/D running at a sample rate of 44.1 kHz. Alternatively, the A/Dcan be disabled and a SP/DIF digital input enabled, allowing PCM digital data from a CD or DVD to be sent directly into theDSP for processing. The two input channels and six output channels all sample at the same time; clock skew betweenchannels is not an issue. By default, the core code reads and writes blocks of 64 samples for each channel of input andoutput; however, this aggregation can be changed to any value between 1 and 80 samples

Other features include buffered serial communication code, which allows you to send and receive data from the serialport. This can be used to control your DSP program with a graphical user-interface on the PC; it can also be used toreport status back to the PC for applications such as speech recognition.

The core code, core.asm (which requires globals.inc , ioregs.inc , and misc.inc ) also initializes the DSP itself. It enables the fractional arithmetic mode for the ALU,programs the wait states for the external memory, and sets the DSP clock to 80 MHz

Testing the six-channel sample code

We will start with a sample application, which simply sends the inputs into the outputs--relaying both the audio inputsfrom the A/D converters to the D/A converters, and any data that comes in on the serial port back to the PC. Tofamiliarize yourself with this sample application, locate a copy of thru6.asm and assemble it.

Once you have done that, start Code Composer. Since we are using the on-chip RAM on the TMS320C549 to hold programcode, we need to map that RAM into program space before we can load our code. This can be done by opening the CPURegisters window (the same one you use to look at the ARx registers and the accumulators) and changing the PMST register to 0xFFE0 . This sets the OVLY bit to 1, switching the internal RAM into the DSP's program memoryspace.

Finally, load the thru6.out file, use Code Composer's Reset DSP menu option to reset the DSP, and run the code. Probe at the connections with thefunction generator and the oscilloscope; inputs and outputs are shown in . Note that output channels 1-3 come from input channel 1, and output channels4-6 come from input channel 2. shows the six-channel board's connector configuration.