LTDC Interface Issue with STM32H7S7I8T6 and SDRAM

[Bharathkumar]

I am currently working with the STM32H7S7I8T6 microcontroller and have selected IS42S16400N-7TL as the external SDRAM.

I would like to interface both SDRAM and an LTDC display with this MCU. However, I’m facing issues because some of the required pins are not available—they are multiplexed (used for dual functions). This is creating a complex configuration problem.

My question is:

• Is it possible to use the same pins for both SDRAM and LTDC functions by synchronizing their usage?
• Can STM32H7S7I8T6 handle such dual-function pin usage without conflicts?
• What is the recommended configuration or workaround for interfacing SDRAM and LTDC simultaneously without pin conflicts?
  Note: The functions RAS (Row Address Strobe) and CAS (Column Address Strobe) are not available in this datasheet.
  If any alternative functions are provided, please mention them.

I need stable SDRAM access for frame buffering and display refresh.

Kindly provide detailed guidance and suggestions to help resolve this issue.

Pin mapping Sheet attached in the attachment.

[Slawekkac]

Hi,

Please see my application and report from quick project with LTDC and SDRAM 16-bit (1 Meg Bits x 16 Bits x 4 Banks). I do not have any conflict.

Regards

[Bharathkumar]

If you have any reference schematic diagrams related to this SDRAM test report, please share them.

[Bharathkumar]

The given test report is acceptable, but I have some questions regarding the compatibility of my designed SDRAM, IS42S16400N-7TL.

Please share the part number you are using, and I would also like to request the schematic diagram for the SDRAM connection circuit.

Additionally, I am sharing the pin details of my SDRAM for your reference:
SDRAM (IS42S16400N-7TL) – Pin Descriptions:

 

Test Report Pin Details

Here are the test report pin connections. Please explain how these can be mapped to the SDRAM interface:

 

Please confirm how these pins match the SDRAM connection requirements or provide guidance on how to connect them correctly. Also, kindly share a schematic diagram that matches this configuration.

[Slawekkac]

Hi,

The XSPI port is prepared for external Flash memory connected by OCTOSPI. I wanted only check possibility connect external Flash memory, SDRAM and LTDC in this version microcontroller.

Best regards

[Bharathkumar]

My design goal is to connect an SDRAM and use LTDC based communication for the display. I have already shared the selected parts in my earlier message. Please check and let me know if it's possible to achieve my requirement.

From your earlier messages, here are the key components you're using:

• Microcontroller: STM32H7S7I8T6

• SDRAM: IS42S16400N-7TL

• Display: 10x12 inch touch display

• LTDC (LCD-TFT Display Controller): Planning to use built in LTDC of STM32H7
  
  

  Microcontroller Capability STM32H7S7I8T6:

  • LTDC Interface: This MCU supports a dedicated LTDC peripheral, which is suitable for driving RGB TFT displays.

  • SDRAM Interface (FMC): The STM32H7 has a Flexible Memory Controller (FMC) capable of interfacing with external SDRAM like the IS42S16400N.

  2. SDRAM – IS42S16400N-7TL:

  • Type: 64Mbit SDRAM (4M x 16)

  • Compatible with FMC: This part is suitable for frame buffer storage when mapped correctly via the FMC.

  3. Display – 10x12 inch touch display:

  • Resolution: Make sure it’s within the LTDC pixel clock and memory bandwidth limits.

  • RGB interface: Confirm that it uses a parallel RGB interface (LTDC is not compatible with MIPI-DSI or HDMI directly).

  • Touch interface: Usually I2C or SPI – handled separately by another peripheral.