Embedded Target for Texas Instruments C6000 DSPs

Using the Overrun Indicator

When your digital signal process application cannot complete the calculations and data manipulations required to yield a result before the available clock cycles expire, your model can generate unreliable data. Failing to complete an algorithm is called overrunning, and is one of the most important errors to identify and eliminate in digital signal processing design and implementation.

The Embedded Target for TI C6000 DSP provides an overrun indicator that you use to notify you when your process is running out of processing time before it completes its tasks. To signal that the algorithm has overrun its limits, the Embedded Target for TI C6000 DSP turns on the external LED on the C6701 EVM and leaves it on until you reset the evaluation module.

Limitations on the Overrun Indicator

In two cases, the overrun indicator does not work:

• In multirate sustems where the rate in the process is not the same as the base clock rate for your model. When this is the case, the timer/scheduler in the Embedded Target for TI C6000 DSP provides the interrupts for setting the model rate and cannot use the LED overrun indication.
• In models that do not include ADC or DAC blocks, the timer/scheduler provides the software interrupts that drive model processing. Again, when the timer/scheduler runs the model, the overrun indicator does not work.

To detect overrun conditions, the generated C code sets and checks a persistent flag during each iteration of the direct memory access (DMA) interrupt service routine.

To indicate an overrun condition on the C6711 DSK, the software turns on all three user-defined LEDs on the board.

Note    Using an LED block to trigger the external LED on the C6701 EVM or the user-defined LEDs on the C6711 DSK, and selecting the Overrun Action option can be confusing when an overrun condition triggers the specified LEDs. The Overrun Action option uses the external LED or user-defined LEDs to signal model conditions. If you are using the overrun indicator, consider not using the LED block to trigger the external LED on the C6701 EVM, or the user LEDs on the C6711 DSK until you stop monitoring your process for overrun conditions.

To enable the overrun indicator, choose one of three ways for the indicator to respond to an overrun condition in your model:

• None--your model does not respond to overrun conditions during processing.
• Continue--when your model runs out of clock cycles before completing enough of the processing algorithm, the overrun indicator turns on the external or user defined LEDs. The model continues to run without pause.
• Halt--when your algorithm runs out of clock cycles before completing the required calculations and manipulations, the model stops executing and turns on the selected LED on the target.

Configuring LED Blocks

Configuring Reset Blocks