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Oblomkov.Ilya
Oblomkov.Ilya
Associate
April 10, 2020
Solved

STM32G474 Flash wait states at 170MHz CPU clock

  • April 10, 2020
  • 8 replies
  • 3280 views

RM0440 Rev 3 (last version) recomend to set 4WS for 170MHz CPU clock

RM0440 Rev 2 recomend to set 8WS for 170MHz CPU clock

ST driver library (STM32G4xx_HAL_Driver) function LL_PLL_ConfigSystemClock_HSE() set 8WS for 170Mhz clock.

Which Flash WS setting is right for 170MHz, 4WS or 8WS?

This topic has been closed for replies.
Best answer by hamdi.najoua

Hello,

The new specification is applicable to all STM32G4 family products.

In fact, the Flash is re-characterized and it is found that the maximum number of wait-states can be reduced from 8 to 4 wait states and so it is possible to achieve 170MHz at only 4 wait-states  which has an interesting impact on the performance.

This new specification will be taken into account in the STM32CubeG4 next version planned for W26.

Best regards,

Najoua.

8 replies

berendi
berendi
Principal
April 10, 2020

I assume that the reference manual was updated for a reason.

The last update of RM0440 is more recent than the latest version of the library.

waclawek.jan
waclawek.jan
Super User
April 10, 2020

This is quite a dramatic change.

It would be nice to hear from ST, what's the reason for this change, and whether it's result of change described in PCN MDG/19/11871 - i.e. whether' it's applicable also for the older revision of the 'G4 chips or not.

@Amel NASRI​ , can we please have a comment on this?

JW

Uwe Bonnes
Uwe Bonnes
Chief
April 10, 2020

Where to get that PCN?

waclawek.jan
waclawek.jan
Super User
April 10, 2020

Some distributors make them available for the commoners, e.g. http://www.anglia.com/registration/pcn_ptn/docs/pcn/st_PCN%20MDG_19_11871.pdf

JW

Singh.Harjit
Singh.Harjit
Senior
April 10, 2020

I found a copy here: https://www.mouser.com/PCN/STMicroelectronics_11871.pdf

Uwe Bonnes
Uwe Bonnes
Chief
April 12, 2020

Hopefully an updated errata sheet appears soon.

hamdi.najoua
hamdi.najouaBest answer
ST Employee
April 16, 2020

Hello,

The new specification is applicable to all STM32G4 family products.

In fact, the Flash is re-characterized and it is found that the maximum number of wait-states can be reduced from 8 to 4 wait states and so it is possible to achieve 170MHz at only 4 wait-states  which has an interesting impact on the performance.

This new specification will be taken into account in the STM32CubeG4 next version planned for W26.

Best regards,

Najoua.

Singh.Harjit
Singh.Harjit
Senior
April 16, 2020

I'd love to hear about data on the performance improvement between the old and new settings for a few relevant workloads - could be the standard workloads, power consumption change, Field oriented control motor control implementation, etc.

hamdi.najoua
hamdi.najoua
ST Employee
April 17, 2020

Yes, we will come of course with more details regarding these aspects.

Najoua.

waclawek.jan
waclawek.jan
Super User
April 16, 2020

Hi Najoua,

Thanks for the comment.

So, does this mean, that the 4WS applies also to the older revisions of the 'G4 chips?

Thanks,

JW

@hamdi.najoua​ 

hamdi.najoua
hamdi.najoua
ST Employee
April 17, 2020

Yes, the 4 WS applies to all G4 products.

Thanks to the new Wait State Matrix, we have + 70% performance increase when code is running from Flash in dual bank mode (64-bit) . 

Regards,

Najoua.

waclawek.jan
waclawek.jan
Super User
April 17, 2020

Thanks, Najoua.

JW

hamdi.najoua
hamdi.najoua
ST Employee
April 29, 2020

​Hello all,

Please refer to this post.

Best regards,

Najoua.

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