TMS320F28374S: PWM period and count values doubt

Jordan Zhou

Tool/software:

Hi,

Just one doubt about PWM period and count values.

In the application code, customer uses PWM base address and offset to get the value of period and count registers, like value=*(0x00004000+0x63).

PWM is up-down mode, with shadow load when count equals to zero.

My question is: what can customer read in value? The active period register value, or shadow value.

We found an issue, without phase shift, customer uses that way to read period and count. Count value is larger than period.

as the issue is very hard to reproduce. There's no way to read the period and count registers through normal register name.

Thanks a lot.

Br, Jordan

11 months ago

0 Allison Nguyen 11 months ago

TI__Mastermind 25280 points

Hello Jordan,

The shadow registers are not memory mapped, so you will not be able to read these values. Hence, when you read from the TBPRD and TBCTR addresses, you read the active registers. Can you elaborate on the nature of the issue?

Best Regards,

Allison

0 Jordan Zhou 11 months ago in reply to Allison Nguyen

TI__Genius 10390 points

Hi,

We did a test, as:

1) Up-down mode, shadow load when cnt=0;

2) Before cnt=0, code write a new value to period register, and then read it, the value is the new one. That means, it's the shadow value, not the active one.

Will you help to confirm please?

Br, Jordan

0 Allison Nguyen 11 months ago in reply to Jordan Zhou

TI__Mastermind 25280 points

Hi Jordan,

My apologies, let me clarify: The register you read/write from/to is determined by the load mode you are using.

In shadow mode, you will read/write from the shadow register (this is what the customer is seeing)
In active mode, you will read/write from the active register

Hope this helps clear up any misunderstanding!

Best Regards,

Allison

0 Jordan Zhou 11 months ago in reply to Allison Nguyen

TI__Genius 10390 points

Thanks a lot.

Br, Jordan

+1 Delaney Woodward 10 months ago in reply to Jordan Zhou

TI__Mastermind 22290 points

Hi Jordan,

I will close this thread but please feel free to make another one if you have any more questions.

Best Regards,

Delaney

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TMS320F28374S: PWM period and count values doubt