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RMcCa
RMcCa
Senior II
May 27, 2020
Solved

F730 flash PSIZE vs. Supply voltage

  • May 27, 2020
  • 6 replies
  • 2635 views

I am a bit confused by the language in the F7 reference manual, section 3.3.5 (RM0431) that describes the flash program/erase parallelism. Does the power supply limit the maximum value of the parallelism or does it limit one to a particular size?

The caption for table 6 is "Table 6 provides the correct PSIZE​ values". Should it say "correct maximum PSIZE values"?

I am asking because i have been writing bytes to the flash with Vcc=3.3V and PSIZE = 0 and its been working fine for a while​, but i wonder if that's only luck and i should switch to 32bit writes. Speed is not an issue in this case.

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Best answer by RMcCa

I know this is minor, but i also found a few copy & paste errors in stm32f7xx_hal_flash.c when i was looking for the answer. The @note in the comments is incorrect for FLASH_Program_Word​, Halfword & Byte.

6 replies

Uwe Bonnes
Uwe Bonnes
Chief
May 27, 2020

"correct maximum PSIZE values" is the right thing

waclawek.jan
waclawek.jan
Super User
May 27, 2020

Uwe,

Can you please quote a source for this?

@Imen DAHMEN​ ,

Can this please be clarified, across all STM32 RMs?

Jan

Uwe Bonnes
Uwe Bonnes
Chief
May 27, 2020

The datasheet STM32F730x8 page 127, table Table 53. Flash memory programming (continued) seems quite clear to me.

I
Imen.D
ST Technical Moderator
May 27, 2020

@RMcCa​ , It's ok for your use case. I confirm, it is the max PSIZE vs Voltage.

I will raise this internally to update all STM32 RMs.

Edit: We suggest to change “Parallelism size�? to “max parallelism size�?.

Best Regards,

Imen

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waclawek.jan
waclawek.jan
Super User
May 27, 2020

Thanks, Imen.

Jan

@Imen DAHMEN​ 

RMcCa
RMcCaAuthor
Senior II
May 27, 2020

Thank you, good to know my code wasn't working by accident.​

RMcCa
RMcCaAuthorBest answer
Senior II
May 27, 2020

I know this is minor, but i also found a few copy & paste errors in stm32f7xx_hal_flash.c when i was looking for the answer. The @note in the comments is incorrect for FLASH_Program_Word​, Halfword & Byte.

I
Imen.D
ST Technical Moderator
May 27, 2020

Hello All,

Thank you for all reported issues.

This is raised internally for correction : even for incorrect comment in the stm32f7xx_hal_flash.c and the wrong max value for 32-bit program operation.

Best Regards,

Imen

In order to give better visibility on the answered topics, please click on 'Best answer' on the reply which solved your issue or answered your question. Thanks
Pavel A.
Pavel A.
May 27, 2020

Pardon me for jumping in.

Does “max parallelism size�? mean “max parallelism size for given voltage"?

That's, lesser parallelisms also work at the same voltage?

And for the voltages - there is a minimal voltage for a given parallelism size?

So answer of the OP question is, it is always OK to write at PSIZE=0 ?

-- pa

RMcCa
RMcCaAuthor
Senior II
May 27, 2020

I believe so.

It would probably clearer if they listed the minimum voltage for each size.​

Piranha
Piranha
Principal III
May 30, 2020

This is a very good question/issue. I was going to ask it some day, but @RMcCa​ did it already. So thank you and thanks to @Imen DAHMEN for clearing it up and fixing documentation.

I can add that I also have been using byte (8-bit) writes at VDD = 3,3 V on F76x for some time in different scenarios on Discovery, Nucleo and custom boards and haven't run into any problems with that.

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