Fractional delay logic of eFlexPWM of MC56F82748

[chuangangxu]

Hi, 

I'm debugging the fractional delay loigc of eFlexPWM of MC56F82748 using P&E mode. The configuration is as attached.

In theory, the duty cycle of PWM45 is closed to PWM23. However the duty cycle of PWM45 is neither closed to PWM23 when PWM_VALUE3 = 250 nor closed to that when PWM_VALUE3 = 249. Actually the falling edge of PWM45 is in the middle of PWM23 when PWM_VALUE3 equals 249 and 250. Is there any configuration wrong i neglected?Attached is the project i am debugging. thanks.

Original Attachment has been moved to: MC56F82748_FRAC_TEST.zip

[xiangjun_rong]

Hi,

Pls refer to the doc from the ticket.

https://community.nxp.com/docs/DOC-106350 

Hope it can help you

BR

XiangJun Rong

[chuangangxu]

Hi, xiangjun,

Thanks for your help!

The fractional part can also be observed in the oscilloscope using my configuration. However the question is the fractional resolution seems not 1/32 of the PWM clock(100MHz) (ie. 312ps). For example, the observed actual duty cycle of (4+ 31/32) is much less than the duty cycle of (5+0/32) and the difference is much higher than 312ps.  

[xiangjun_rong]

Hi,

Do you pay attention that the bit 11_15 of PWMA_SMnFRACVAL1 register are valid?

BR

Xiangjun Rong

[chuangangxu]

Hi,

Many thanks!

I have already solved this issue. The resolution issue is caused by the register circled below. I can not find where to set this OCCS_DIVBY[PWM_DIV2] to 1 using P&E mode.

But i modify the register directlly and make it correct.

发件人: xiangjun.rong

发送时间: 2016年12月16日 15:27

收件人: Chuanggang Xu <Chuangang.Xu@belf.com>

主题: Re: - Re: Fractional delay logic of eFlexPWM of MC56F82748

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Re: Fractional delay logic of eFlexPWM of MC56F82748

reply from xiangjun.rong<https://community.nxp.com/people/xiangjun.rong?et=watches.email.thread> in Digital Signal Controllers - View the full discussion<https://community.nxp.com/message/861166?commentID=861166&et=watches.email.thread#comment-861166>

[xiangjun_rong]

Hi, Chuangang,

Do you want to use nano-edge PWM mode for eFlexPWM module so that you can generate the fractional duty cycle PWM signal for example setting the PWM value5 as 249 plus 31/32? If it is the case, you have to enable the internal PLL of eFlexPWM module, it is complicated.

Hope it can help you

BR

XiangJun Rong

[xiangjun_rong]

Hi,

Pls refer to the ticket.

https://community.nxp.com/docs/DOC-332423 

BR

XiangJun Rong

[chuangangxu]

Hi, Xiangjun,

There seems no similar registers and any decription of the internal PLL of eflexPWM module in the datasheet or the reference manual of MC56F82748.