Reconfigure SPI from SYSCLK7 (default) to other SYSCLK

Alon Slapak

Hello,

For debugging purpose, I'd like to slow the SPI clock to below SYSCLK7 /256 . SYSCLK7 is SYSCLK/6=166.66M and the 256 is the SPI max PRESCALE.

As far as I am concerned, this can be done by reconfiguring the SPI to be clocked by SYSCLK6 or SYSCLK9 and instead of by it's default SYSCLK7 (I assume that "default" means also that I can deliberately change it) .

How can I do it?

Thanks, Alon.

over 11 years ago

0 Raja over 11 years ago

TI__Guru* 81335 points

Hi Alon,

Could you please provide the part number of the DSP device?

Thanks.

0 Alon Slapak over 11 years ago in reply to Raja

Prodigy 250 points

Hi Rajasekaran.

Sure. TMS320C6678AXCYP25.

Thanks, Alon.

0 Bill Taboada over 11 years ago

TI__Mastermind 42545 points

Hi Alon,

The SPI subsystem is always clocked with SYSCLK7. This cannot be reconfigured.

Regards, Bill

0 Alon Slapak over 11 years ago in reply to Bill Taboada

Prodigy 250 points

Thank you Bill.

kindly confirm that SPI minimum rate is therefore ~653kHz, or better, propose an alternative to use C6678's SPI with lower clock rate, say, 100 kHz.

Alon,

0 Bill Taboada over 11 years ago in reply to Alon Slapak

TI__Mastermind 42545 points

Hi Alon,

The SPI is based on the frequency selected for the core. During normal operations the minimum frequency is 800MHz. Assuming that frequency, the minimum SPI clock frequency is (800MHz/6)/256 = 520.833KHz. If you want to operate your SPI interface at a lower frequency, you would have to use external logic to create a bridge. We can't support frequencies that slow with the SPI.

Regards, Bill

0 Alon Slapak over 11 years ago in reply to Bill Taboada

Prodigy 250 points

Hi Bill.

Thank you. Because it is for debugging purpose only, we have succeeded to operate the DSP (on the EVM. We didn't test on our board) with much lower frequency by setting the definitions of PLL1_M and PLL1_D in the gel file to 2 and 0 respectively. This gave us the opportunity to find the fault with the SPI communication and now it works also with the normal frequency.

Thanks for the prompt reply, Alon.

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Reconfigure SPI from SYSCLK7 (default) to other SYSCLK