Hi,
We are using the STM32U5A9J-DK board and are trying to achieve Read-While-Write (RWW) functionality. The flash chip we are using supports RWW.
Earlier, as per [this post](post link), we learned that to achieve RWW, we need two OSPI instances, namely OSPI1 and OSPI2.
Here are the configurations for both OSPI1 and OSPI2 in STM32CubeIDE:
- OSPI1 Configuration:
- OSPI2 Configuration:
We tested the setup and observed the following:
- Using OSPI1, we can successfully perform read, write, and erase operations on the flash memory.
- However, when attempting to access the flash memory with OSPI2, we are unable to perform these operations.
Questions:
- Is our current configuration of OSPI1 and OSPI2 (in multiplexed mode) correct for achieving RWW?
- Can you provide an example application where RWW is implemented using OSPI1 and OSPI2?
We would greatly appreciate any insights or guidance on this issue.
Thank you!
Hi @KDJEM.1
Thank you for your response and the suggestions provided.
Unfortunately, the issue is not resolved after configuring the chip select for OSPI2.
As per the schematic, the flash's chip select is connected to PORT1. When we configure the chip select option in OSPI2 as PORT1 NCS, we must disable it in OSPI1. In this scenario:
- We can access the flash using the OSPI2 instance, but OSPI1 access stops working.
- Similarly, when OSPI1 is enabled, OSPI2 access fails.
This means we can access the flash using either OSPI1 or OSPI2, but not both simultaneously. Since RWW functionality requires both instances to work concurrently, we are facing a roadblock.
The example you shared is for a different development board. We tried replicating the configurations on our platform (STM32U5A9J-DK) but still cannot access the flash with both OSPI1 and OSPI2 instances simultaneously.
We suspect that we may be missing something in the configuration.
Could you confirm whether our current configuration aligns with the requirements for RWW? Additionally, is there any application project or reference specifically for STM32U5A9J-DK where RWW has been demonstrated to work?
Our octal SPI nor flash memory supports RWW. Can you confirm the STM32U5A9J-DK supports RWW ?
We appreciate your guidance and support in resolving this issue.
Hi @KDJEM.1 ,
Thank you for your response.
As mentioned, we understand that RWW needs to be supported by the Octal SPI NOR flash memory, which is true in our case. We are using ISSI Octal Flash Memory that supports RWW. We have connected the ISSI flash memory in place of the Macronix flash on the STM32U5A9J-DK as shown in the attached image.
The RWW example provided by you is for the STM32H7S78-DK, which uses an xSPI IO Manager. However, our board (STM32U5A9J-DK) is equipped with an OSPI IO Manager.
Referring to the AN5050 (page 25):
- The xSPI IO Manager delivers one NCS signal along with a CSSEL control signal.
- It also allows selecting the same NCS for both XSPI_1 and XSPI_2 using the configuration.
XSPI Configurations for RWW example that you have given :
- hxspi1.Init.MemorySelect = HAL_XSPI_CSSEL_NCS1;
hxspi2.Init.MemorySelect = HAL_XSPI_CSSEL_NCS1;
sXspiManagerCfg.nCSOverride = HAL_XSPI_CSSEL_OVR_NCS1;
However, the OSPI IO Manager does not provide these options:
- When selecting Port1 NCS for OSPI1, it does not allow the same Port1 NCS for OSPI2.
- Instead, we either need to disable Port1 NCS for OSPI2 or switch to Port2 NCS.
As a result:
- If OSPI1 is configured to use Port1 NCS, OSPI2 stops working.
- Similarly, if OSPI2 is configured to use Port1 NCS, OSPI1 stops working.
This limitation seems to make it impossible to access the ISSI flash memory from both OSPI1 and OSPI2 instances simultaneously in multiplexed mode using the OSPI IO Manager.
Could you please confirm whether our understanding is correct?
Thank You .
