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Hi,
I want to use the HRPWM module for design. After reading the mannul I found that DCAEVT1.sync and DCBEVT1.sync can still be used in HRPWM (as shown in Fig.18-84).
But I also found :
"When high-resolution period mode is enabled, an EPWMxSYNC pulse will introduce +/- 1 - 2 cycle
jitter to the PWM (+/- 1 cycle in up-count mode and +/- 2 cycle in up-down count mode). For this
reason, TBCTL[SYNCOSEL] should not be set to 1 (CTR = 0 is EPWMxSYNCO source) or 2 (CTR =
CMPB is EPWMxSYNCO source). Otherwise, the jitter will occur on every PWM cycle with the
synchronization pulse.
When TBCTL[SYNCOSEL] = 0 (EPWMxSYNCI is EPWMxSYNCO source), a software
synchronization pulse should be issued only once during high-resolution period initialization. If a
software sync pulse is applied while the PWM is running, the jitter will appear on the PWM output at
the time of the sync pulse."
I wonder if the DCAEVT1.sync or DCBEVT1.sync cause a Jitter on HRPWM?
There will be a DCEVT.sync signal during each period (but I don't know when it will occur) and I want to use this signal to set the CTR to zero or other value (through loading the phase )
But there is:
TBPHSHR must not be used. Instead TRREM (HRPWM remainder register) must be used to mimic
the functionality of TBPHSHR."
So will the phase value loaded without jitter?
Thanks!
If there is a sync every period the yes you will see the jitter on HRPWM.
Are you using HR DUTY or HR PERIOD?
Hi,
There is a sync every period......
I will use HR Duty, but the period depens on the sync signal.
So the jitter can not be avoided?
Thanks
I think not, I'll set TBPRD at a large value......the EPWM frequeny depends on the sync signal to reset the CTR to zero or a certain value
But I'll use CMPAHR and CMPBHR, I also want to use HR phase to achieve the above function "reset CTR"
I'll use sync signal to set EPWM to high, and CMPAHR or CMPBHR set EPWM to low, then the sync signal comes again and repeat
If you need HR PHASE and there is a sync signal in every period, you will see the jitter.
So I can't avoid the jitter under any case, even if I set the phase to zero ?
And why that jitter occurs? Is it because the time when sync occurs doesn't match with the TBPRD?
Well if you dont use TBPRDHR or TBPHSHR, you should be able to get high resolution duty. But that means no TBPHSHR or TBPRDHR and HRPE disabled.
The jitter is becuase when using high resolution period, the remainder of the period high resolution mode is always compensated. When a sync occurs, the first cycle must reset the values causing jitter.