CCS/TMS320F28075: EPWM1 module of 100pin chip

Weijing Du

Tool/software: Code Composer Studio

Part of the previous questions has been solved by myself, but still have issues about the EPWM timing. So, I modified the questions as follows. Sorry for the inconvenience!

I am using the 100pin 28075 chip right now. Since the EPWM1 module is not pined out in this version, I tested to use EPWM7 module instead. The SYNCIN source is EXTSYNCIN1 by configuring SyncSocRegs.SYNCSELECT.bit.EPWM7SYNCIN = 5. But the delay between the rising edge of EXTSYNCIN1 and EPWM7A sets is 80ns. Why the delay time is so long? The EPWM clock frequency is 100MHz.

I have used TMS320F28027 before with 60MHz clock frequency in the same way, and the delay time is 70-90ns. So, I feel maybe something is wrong? or the propagation delay of muxes circled out in the figure below is too long? Where can I find the propagation delay information of the muxes circled out in the following picture?

The code is attached below for your convenience. Thank you in advance!

5531.28075_TEST_EPWM_EXTSYNC.zip

over 8 years ago

0 Weijing Du over 8 years ago

Intellectual 460 points

I modified the questions, sorry for the inconvenience

0 Chen Jiang ti over 8 years ago in reply to Weijing Du

TI__Genius 16085 points

Hi Weijing,

Thank you for your detailed question. Your thread has been assigned to the C2000 experts and should get feedback soon.

Best regards,
Chen

0 Cody Watkins over 8 years ago

TI__Mastermind 42195 points

Weijing,

The muxes you have circled have a delay of 0.

When using the external sync in you can expect a delay of 6-7 cycles, so your delay sounds reasonable. If your are worried about that delay you can remove synchronization on the external SYNCI pin and you could save 1 or 2 cycles.

Hope it helps,
Cody

0 Weijing Du over 8 years ago in reply to Cody Watkins

Intellectual 460 points

Thank you for your reply!

In the code, I already removed the synchronization on the external SYNCI pin by configuring:

GpioCtrlRegs.GPCQSEL2.bit.GPIO89 = 3; // Asynch input GPIO89

But still have 80ns delay, which is 8 cycles. So, that's why I am thinking the delay is too long

0 Cody Watkins over 8 years ago in reply to Weijing Du

TI__Mastermind 42195 points

Weijing,

This is a different device than the quoted 6-7 cycles I had mentioned. It's very likely that F28075 requires an extra cycle. Please read this thread and come back with any question you may have: https://e2e.ti.com/support/microcontrollers/c2000/f/171/p/313720/1098695

Regards,
Cody

0 Weijing Du over 8 years ago in reply to Cody Watkins

Intellectual 460 points

Thank you for your reply!

In 28075, I use InputXBar to connect the EXTSYNCIN signal to the EPWM7 module. Do you know the propagation delay for the InputXBar?

0 Cody Watkins over 8 years ago in reply to Weijing Du

TI__Mastermind 42195 points

Weijing,

the path through the InputXBar is asynchronous, and will result in a small delay that is acceptable for most applications. After the signal passes through to the sync chain it is all cycle guaranteed.

Regards,
Cody

0 Weijing Du over 8 years ago in reply to Cody Watkins

Intellectual 460 points

Thank you for your reply!

Based on my test, the delay of input Xbar is around 50ns, is it reasonable?

0 Cody Watkins over 8 years ago in reply to Weijing Du

TI__Mastermind 42195 points

I am looking into what this number should be, sorry for the delay.

Regards,
Cody

0 Cody Watkins over 8 years ago in reply to Cody Watkins

TI__Mastermind 42195 points

Weijing,

I have requested that design simulations be performed. However, this will take some time. The initial comment from the designer was that you are seeing a longer than expected delay.

Regards,
Cody

0 Cody Watkins over 8 years ago in reply to Cody Watkins

TI__Mastermind 42195 points

Weijing,

i just wanted to post back here, I have received confirmation that this is in the designers queue. I don't have an estimate when it will be completed.

Regards,
Cody

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CCS/TMS320F28075: EPWM1 module of 100pin chip