TMS320F28377D: CMPA updating in CLA

Hello,
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Regards
Himanshu

Hello, Yan

This is system dependent.  There is nothing in the MCU to insure the update will be within the current cycle.  It will depend on

• When/how the SDFM is triggered
• If the CLA is already busy or if it is idle
• How long the CLA computation is before the update to CMPA is made 

The SDFM can be synchronized to PWM11 or 12 as shown in the SDFM block diagram in the device-specific technical reference manual (TRM).   This feature can be used in the design to synchronize the SDFM to a PWM cycle.  

I hope this helps.  If my response resolved your question, please click the "verified answer" button.

thank you

Lori

Yan,

I wanted to add more information. The best, and safest way, to update CMPA at a specific time is to use the shadow register feature. This is documented in the description of the CMPA and the CMPCTL register descriptions in the device specific TRM.

I hope this helps. If my response resolved your question, please click the "verified answer" button.

Regards
Lori

Dear Lori Heustess:
This question(about "CLA and PWM CPMA") was raised by me.
In my program, I have used the "shadow mode" and enabled the "shadow register" as below:
(*ePWM[n]).CMPCTL.bit.SHDWAMODE = CC_SHADOW;
shadow→active will be done on the event for example CTR = PRD event.
That's no problem!

My question is：
When I use the shadow register, as you know, the true active register will not be updated immediately.
Is there a "deadline" that I must update the CMPA ahead of the event:shadow→active?(for example the CTR = PRD event)
If I missed some "deadline", and updated the CMPA after the "deadline", then the true active one
have to update untill next event.

If there is a deadline, so I want to know how long it must take to in advance?

My program like below:
__attribute__((interrupt)) void Cla1Task1 ( void ) //triggered by SINC
{
.....; //code here
Delay(x); //delay x us
//I read the curTime from Debug and adjust the "x" ensure the "PWM7on→bit.CMPA" as late as possible.
CurTime = EPwm7Regs.TBCTR;
//If below executed just 1 system clk before CTR = PRD event , can we ensure value updated on current event?
EPwm7Regs.CMPA.bit.CMPA =PWM7on;
}

Thank you very much!

Dear Lori Heustess:
This question(about "CLA and PWM CPMA") was raised by me.
In my program, I have used the "shadow mode" and enabled the "shadow register" as below:
(*ePWM[n]).CMPCTL.bit.SHDWAMODE = CC_SHADOW;
shadow→active will be done on the event for example CTR = PRD event.
That's no problem!

My question is：
When I use the shadow register, as you know, the true active register will not be updated immediately.
Is there a "deadline" that I must update the CMPA ahead of the event:shadow→active?(for example the CTR = PRD event)
If I missed some "deadline", and updated the CMPA after the "deadline", then the true active one
have to update untill next event, so delay a cycle.

If there is a deadline, so I want to know how long will it take to in advance?

My program like below:
__attribute__((interrupt)) void Cla1Task1 ( void ) //triggered by SINC
{
.....; //code here
Delay(x); //delay x us

//I read the curTime from Debug and adjust the "x" to ensure the "PWM7on→bit.CMPA" as late as possible.
CurTime = EPwm7Regs.TBCTR;
//If this code executed just 1 sys_clk before CTR = PRD event , can we ensure the value updated on current event?
EPwm7Regs.CMPA.bit.CMPA =PWM7on;
}

Thank you very much!

Hello,

I haven’t heard from you for a few days, so I’m assuming you were able to resolve your issue.

If this is the case, please press the "verified answer" button to close the thread. 

If this isn’t the case, please click the "This did NOT resolve my issue" button and reply to this thread with more information. If this thread locks, please click the "Ask a related question" button and in the new thread describe the current status of your issue and any additional details you may have to assist us in helping to solve your issues.

Regards,
Lori