TMS320F28P650DK: How to route CMPSS2_CTRIPH to EPWM1 trip zone signal

Hi Prashant,

There is no direct path from the CMPSS to the trip zone submodule — you must route through the ePWM X-BAR and Digital Compare submodule [1][2]. Here's the complete signal chain:

Signal Routing Path

CMPSS2_CTRIPH → ePWM X-BAR (MUX) → TRIP4 → Digital Compare (DCAH) → DCAEVT1 → Trip Zone → Force EPWM1 outputs safe

Step-by-Step Configuration

1. Configure the ePWM X-BAR

Route CMPSS2_CTRIPH to one of the trip inputs (TRIP4–TRIP12). For CMPSS2, use the appropriate MUX position from the ePWM X-BAR Mux Configuration Table in the TRM [3][4]:

// Route CMPSS2_CTRIPH to EPWM X-BAR TRIP4
XBAR_setEPWMMuxConfig(XBAR_TRIP4, XBAR_EPWM_MUX02_CMPSS2_CTRIPH);
XBAR_enableEPWMMux(XBAR_TRIP4, XBAR_MUX02);

2. Configure EPWM1's Digital Compare Submodule

Select TRIP4 as the Digital Compare A High (DCAH) input and define the event condition [6][7]:

// Select TRIP4 as DCAH input via trip combination
EPWM_selectDigitalCompareTripInput(EPWM1_BASE,
EPWM_DC_TRIP_TRIPIN4, EPWM_DC_TYPE_DCAH);

// Define DCAEVT1: trigger when DCAH goes high
EPWM_setTripZoneDigitalCompareEventCondition(EPWM1_BASE,
EPWM_TZ_DC_OUTPUT_A1, EPWM_TZ_EVENT_DCXH_HIGH);

3. Configure the Trip Zone Submodule

Set the trip zone to respond to DCAEVT1 with a one-shot trip (appropriate for overcurrent protection) [8]:

// Enable DCAEVT1 as one-shot trip source
EPWM_enableTripZoneSignals(EPWM1_BASE, EPWM_TZ_SIGNAL_DCAEVT1);

// Set action: force EPWM1A and EPWM1B low on trip
EPWM_setTripZoneAction(EPWM1_BASE,
EPWM_TZ_ACTION_EVENT_TZA, EPWM_TZ_ACTION_LOW);
EPWM_setTripZoneAction(EPWM1_BASE,
EPWM_TZ_ACTION_EVENT_TZB, EPWM_TZ_ACTION_LOW);

Summary Table

This creates a fast, hardware-based protection path that forces PWM outputs to a safe state immediately when the comparator detects overcurrent — no CPU intervention required [9]. Reference design TIDM-02014 provides a complete implementation example [10].

To help refine this recommendation, it would be helpful to know:

• Whether you need one-shot (latched until software clears) or cycle-by-cycle (auto-clears each PWM cycle) trip behavior
• The desired output state on trip (force low, force high, or high-impedance)
• Whether you're using SysConfig or direct register/API configuration

1. TMS320F28P65x TRM - CMPSS Block Diagram
2. SPRAD12A - Routing CMPSS to Trip Zone
3. TMS320F28P65x Datasheet - CMPSS Connectivity
4. SPRACY3 - CMPSS to EPWM X-BAR Configuration
5. E2E - F28P65x requires explicit EPWMXBAR configuration
6. TMS320F28P65x TRM - Digital Compare Submodule
7. C2000 Academy - ePWM Module
8. TMS320F28P65x TRM - Trip Zone Submodule
9. SPRACX0 - X-BAR and ePWM DC Module Interface
10. E2E - CMPSS to PWM XBAR routing for trip zones

Best Regards,

Zackary Fleenor

Hi Prashant,

Glad the configuration worked. :)

Based on your follow-up answers, here's a summary of your current setup and guidance for your future cycle-by-cycle implementation.

Current Configuration (Confirmed Working)

Your one-shot trip with force-low output via SysConfig follows the correct signal chain:

CMPSS2_CTRIPH → ePWM X-BAR (TRIP4) → Digital Compare (DCAH → DCAEVT1) → Trip Zone (One-Shot, Force Low)

This creates a hardware-based overcurrent protection path that forces PWM outputs low immediately—no CPU intervention required [1][2][3].

Critical F28P65x note: This device requires explicit EPWMXBAR configuration in SysConfig. Unlike other C2000 devices, the crossbar connection is not implicit—if you ever port to another project, ensure the EPWMXBAR instance is added [4].

Future: Cycle-by-Cycle Trip for PSFB Peak Current Mode Control

When you transition to cycle-by-cycle (CBC) for your Phase-Shifted Full-Bridge control, the key differences are:

In SysConfig, this is a straightforward change in the Trip Zone configuration section—switch from one-shot to CBC trip source for DCAEVT1.

Reference

The TIDM-02014 reference design provides a complete implementation example of CMPSS-based overcurrent protection with ePWM trip zones that you can reference for both one-shot and CBC configurations [6].

To help refine the cycle-by-cycle recommendation when you're ready:

• What PWM frequency and count mode (up-count or up-down) will you use for the PSFB?
• Whether you need blanking window functionality to filter noise during switching transitions
• Whether CMPSS DAC synchronization with ePWM events is needed for dynamic threshold adjustment

1. TMS320F28P65x TRM - Digital Compare Submodule
2. SPRAD12A - Routing CMPSS to Trip Zone
3. TMS320F28P65x Datasheet - CMPSS Connectivity
4. E2E - F28P65x requires explicit EPWMXBAR configuration
5. E2E - TMS320F28P659DK-Q1 Trip Zone Peak Current Control
6. SPRACX0 - X-BAR and ePWM DC Module Interface

Best Regards,

Zackary Fleenor