DM643x PWM - Configure DM643x DSP Event Manager to generate PWM waveforms

Library

Embedded Coder/ Embedded Targets/ Processors/ Texas Instruments C6000/ DM6437 EVM

Embedded Coder/ Embedded Targets/ Processors/ Texas Instruments C6000/ Scheduling

Description

This block configures any one of the three PWM modules on the DM6437; each module has one output. The PWM module's clock cycles depend on the DM6437's 27 MHz input clock, and are not affected by the DM6437's PLL module. Upon startup, the PWM module uses the Initial waveform period and Initial duty-cycle values. Inputs to the waveform period port, T, and the duty-cycle port, W, can change those values while the application is running.

Dialog Box

The PWM block dialog box comprises four tabs:

• Timer — Select the PWM module, and configure the initial waveform.

• Outputs — Configure the initial duty cycle.

• Logic — Configure the control logic.

• Mode — Configure one-shot or continuous operation.

The following sections describe the contents of each tab in the dialog box.

Timer

Module

Select the PWM module for this block. All the parameter settings in this block configure the registers of the PWM module selected.

Initial waveform period

Set the initial period of the PWM waveform. The waveform period applied at the input port, T, changes this value. The range of acceptable values is 0.000000296 to 79.536431370 seconds or 8 to 2³¹-1 clock cycles. These ranges depend on the 27 MHz clock frequency and the width of the 32-bit register.

Waveform period units

Set the unit of measure of the waveform period to Seconds or Clock cycles. This setting applies to both the Initial waveform period and the waveform period input, T. Clock cycles depend on the DM6437's 27 MHz input clock.

Outputs

Initial duty-cycle

Set the initial duty-cycle of the PWM. The duty-cycle applied at the input port, W, changes this value. The range of acceptable values is 0 to 100 percent or 8 to 2³¹-1 clock cycles. These ranges depend on the 27 MHz clock frequency and the width of the 32-bit register.

Duty-cycle units

Set the unit of measure of the duty-cycle to percentage or clock cycles. This setting applies to both the Initial duty-cycle and the duty-cycle input, W. Clock cycles depend on the DM6437's 27 MHz input clock.

Logic

PWM control logic

Control the state of the PWM output while it is inactive and the polarity of the PWM waveform when it is active:

• Inactive Low (Low to High): When the PWM output is inactive, the output remains low. When it is active, the first phase is low, and the second phase is high.

• Inactive Low (High to Low): When the PWM output is inactive, the output remains low. When it is active, the first phase is high, and the second phase is low.

• Inactive High (Low to High): When the PWM output is inactive, the output remains high. When it is active, the first phase is low, and the second phase is high.

• Inactive High (High to Low): When the PWM output is inactive, the output remains high. When it is active, the first phase is high, and the second phase is low.

Mode

PWM Mode

Set the mode to one-shot or continuous. One-shot repeats the waveform for the number of periods given by repeat value and then, if interrupts are enabled, generates an interrupt at the end of operation. Continuous repeats the waveform infinitely and generates an interrupt, if enabled, every period.

Repeat Value

Set the repeat value if PWM Mode is set to One-shot. The PWM module outputs the waveform the specified number of times +1.

Interrupt enable

Enable the PWM module to generate an interrupt.

In one-shot mode, the PWM module generates an interrupt when number of periods given by Repeat value have been completed.

In continuous mode, the PWM module generates an interrupt during each period signaling that it is safe to set values for the subsequent waveform period and duty cycle.

References

For detailed information on the PWM module, see TMS320DM643x DMP Pulse-Width Modulator (PWM) Peripheral User's Guide, Literature Number SPRU995, available at the Texas Instruments Web site.

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