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FMC distrubed when using high speed of LTDC

fasyr.1
Associate II

I'm using STM32H743ZITX for displaying a 1280X720 LCD, first i set FMC frequency to 266 MHz and LTDC frequency to 20, everything was running well and i can read data from SDRAM was same as what i've written to it, but problems come when i set the frequency of LTDC to 64 MHz, when i read data from the SDRAM the datas was being random and didnt same anymore as what i've written before.

could you guys please share your experiece if you have this problem or any suggestion what i have todo?

here i share my clock configuration on STM32CUBEIDE

0693W00000aHNNLQA4.jpg

3 REPLIES 3
KDJEM.1
ST Employee

Hello @fasyr.1​ ,

According to the datasheet DS12110 and precisely 7.3.17 FMC characteristics Section, for the STM32H743ZIT6 rev V the FMC_SDCLK maximum are:

0693W00000aHcWcQAK.png So try to use a FMC_SDCLK value with respect these conditions.

Please let me know if the problem is solved.

Thank you.

Kaouthar

To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

but i read the other datasheet which is more new revision(rev 8) below.

it told that the FMC frequency is up to 300 MHz for STM32h743

0693W00000aHSvhQAG.png

KDJEM.1
ST Employee

Hello @fasyr.1​ ,

Yes you are right, the FMC frequency is up to 300MHz for STM32H743.

But the max FMC_SDCLK we can run SDRAM depends on the VDD and on the capacitor value:

• For 2.7 V<VDD<3.6 V: FMC_SDCLK =110 MHz at 20 pF

• For 1.8 V<VDD<1.9 V: FMC_SDCLK =100 MHz at 20 pF

• For 1.62 V<DD<1.8 V, FMC_SDCLK =100 MHz at 15 pF

Thank you.

Kaouthar

To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.