FMC memory in fmc display

[Patryk_Kucia]

hello, I have a display configured for FMC but I would like to add a framebuffer to the RAM memory, unfortunately the MCU memory is not enough (the display resolution is 480x800) so I have to add external RAM. My question is how to do it since I am already using FMC for the display. Can I connect RAM to the same pins?

[SofLit · Accepted solution]

Hello,

You will be using the same Address/Data/ NOE/NWE pins and you need to drive your SRAM with another chip enable. The chip enable FMC_NE is driven according to the access address :

BANK1 (256MB) needs to be used which in turn split into 4x64MB. Each access to a block of 64MB will activate the corresponding FMC_NEx pin FMC_NE1 to FMC_NE4.

Hope I answered your question.

[Patryk_Kucia]

Thank you, so FMC_NEX works in parallel with another enable? Do I have to stop refreshing the display when I want to modify something in the buffer? Additionally, will this solution work OK and does double buffer make sense in this case?

[SofLit]

Thank you, so FMC_NEX works in parallel with another enable? 

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Each enable is activated at a time. FMC_NEx is activated automatically by the FMC controller according to the description I provided previously.

As example, you can refer to the STM3240G-EVAL board schematics which is using LCD and SRAM that both are connected on FMC interface: 

Do I have to stop refreshing the display when I want to modify something in the buffer? 

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You are using LCD over FMC, and normally, these kind of display devices have their own controllers with an internal RAM that holds the display buffer. I don't think you need to stop refreshing the display.

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Additionally, will this solution work OK and does double buffer make sense in this case?

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I think it depends on your application.