SNIU028D February 2016 – September 2020 UCD3138 , UCD3138064 , UCD3138064A , UCD3138128 , UCD3138A , UCD3138A64
These registers select what DPWM signals are used to trigger DAC control functions in the Front end, Ramp and Dither. The selected signals are also used when the Ramp Module is used for Sync FET ramps. Two signals can be used:
Frame sync occurs at the beginning of the DPWM period. It always occurs whenever the DPWM is running. DPWMA and DPWMB are dependent on the actual rising edges of DPWMA and DPWMB. If no DPWM pulse is occurring, then the trigger will not take place. DPWMA_F and DPWMB_F are used. These are the signals coming out of the Fault Block, as shown in Figure 2-1. Anything in the Timing or Fault modules which prevents DPWMA and DPWMB from going high will prevent triggering of the Front End by these signals. Anything further down in the signal chain, such as the Intra Mux or the Edge Generator will have no effect at all.
This trigger should not be confused with the sample trigger, which triggers the EADC conversion. Ideally the DAC control function should be triggered just after the end of the EADC conversion to allow maximum DAC settling time. For DAC settling time, please refer to the UCD3138 device datasheet.
The FECTRLxMUX registers also permit using the Nonlinear Select registers in the Filter to set the step points for Automatic Gain Shifting in the Front End.
For exact FECTRLxMUX bit assignments, see: Section 5.15.1, Front End Control 0 Mux Register (FECTRL0MUX).