SPRUJ53C April 2024 – February 2025 TMS320F28P550SG , TMS320F28P550SJ , TMS320F28P559SG-Q1 , TMS320F28P559SJ-Q1
The repeater module can delay the initial trigger by a specified number of SYSCLK cycles. This feature can be used in combination with oversampling or undersampling modes, or as a standalone delay by setting NSEL = 0. The phase delay does not affect the timing between subsequent repeated oversampled triggers—the phase delay only delays the initial trigger. When PHASE = 0, the initial trigger arrives at the same time as an unmodified trigger. Figure 15-6 shows an example of phase delay combined with oversampling. Figure 15-7 shows an example of a standalone phase delay with a single SOC trigger.
Phase delay enables the application to tie the trigger start point to an ePWM event while allowing for a necessary sampling delay (for example, settling time). In addition, when phase delay is combined with oversampling functionality, a single trigger can generate an interleaved burst of conversions across multiple ADCs. To achieve this, set PHASE in increments of (tsample/n_interleaved_ADCs). Figure 15-8 shows an example of interleaving 12 samples across 3 ADCs.
TRIGGER = ePWM SOCA, NSEL = 3, PHASE = 100, MODE = Oversampling, SPREAD = 0
Figure 15-6 Oversampled ADC Trigger Example with Phase DelayTRIGGER = ePWM SOCA, NSEL = 0, PHASE = 100, MODE = (either), SPREAD = (don't care)
Figure 15-7 ADC Trigger Example with Phase DelayTRIGGER = ePWM SOCA, NSEL = 3, MODE = Oversampling, PHASE = (varies per ADC), SPREAD = 0
Figure 15-8 ADC Interleaved Trigger Example (12 Samples Across 3 ADCs)