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Original question:

TMS320F28377D: epwm synchronization

TMS320F28379D: About ePWM synchronization chain

O.H
Mastermind 7100 points

Part Number: TMS320F28379D

Hi experts,

1. TMS320F2837xD Dual-Core Microcontrollers Technical Reference Manual (Rev. K)
Section: 15.4.3.3 Time-Base Counter Synchronization

Q1-1. Maximum ePWM synchronization chain length
I understand that the maximum ePWM synchronization chain length is 4. More specifically, if I configure:
SYNCSELECT.EPWM4SYNCIN = EPWM1SYNCOUT, and
SYNCSELECT.EPWM7SYNCIN = EPWM4SYNCOUT,
would it be correct that I must not configure a propagation path such as:
EPWM1 → EPWM4 → EPWM7 → EPWM8 → EPWM9
because this would exceed the maximum allowed chain length?
Based on the following sentence in Section 15.4.3.3:
“When configuring the sync chain propagation path using the SYNCSEL registers, make sure that the longest path does not exceed four ePWM/eCAP modules.”

Q1-2. Parallel synchronization chains (multiple branches)
If the maximum chain length is 4, for example using EPWM1 CTR=zero as the SYNCOUT source, is it acceptable to configure multiple synchronization chains in parallel as shown below?
EPWM1 → EPWM2 → EPWM3
EPWM1 → EPWM4 → EPWM5 → EPWM6
EPWM1 → EPWM7 → EPWM8 → EPWM9
EPWM1 → EPWM10

2. TMS320F2838x Real-Time Microcontrollers With Connectivity Manager TRM (Rev. F)
Section: 26.4.3.3 Time-Base Counter Synchronization

Q2-1. Maximum ePWM synchronization chain length
Would it be correct to interpret that, in F2838x, the synchronization chain length limitation no longer applies (i.e., the “maximum chain length” restriction is removed), because SYNCIN sources can be flexibly selected via PWMSYNCINSEL?

Best regards,
O.H

  • +1
    TI__Prodigy 630 points

    Hi O.H,

    Q1-1: Maximum chain length of 5 modules (EPWM1 → EPWM4 → EPWM7 → EPWM8 → EPWM9)

    Not allowed. The F28377D has a maximum sync chain length of 4 modules. This chain has 5 modules and violates the design rule in TRM Section 15.4.3.3. The limitation exists due to propagation delay accumulation through the chain.

    Q1-2: Parallel synchronization chains from EPWM1

    Yes, this is acceptable. The 4-module limit applies to each individual path, not the total number of synchronized modules. Your configuration is valid because each branch is ≤ 4 modules:

    • EPWM1 → EPWM2 → EPWM3 (3 modules)
    • EPWM1 → EPWM4 → EPWM5 → EPWM6 (4 modules)
    • EPWM1 → EPWM7 → EPWM8 → EPWM9 (4 modules)
    • EPWM1 → EPWM10 (2 modules)

    Parallel branching is explicitly supported by the SYNCSELECT architecture.

    Q2-1: F2838x synchronization chain limitations

    The F2838x provides more flexible routing via PWMSYNCINSEL. It uses the EPWMSYNCINSEL register, allowing any ePWM SYNCOUT or eCAP signal to be selected as the SYNC input for any ePWM module. No daisy-chain restrictions eliminates the routing constraints of the F2837x.

    Regards,
    Harisyam

  • 0 in reply to Harisyam P V
    Mastermind 7100 points

    Hi Harisyam,

    Thank you for your reply. I uderstood.

    Best regards,
    O.H