stm32U585 + 2 x APS25608N OSPI - speed problems
Hai All!
I use 2 pieces of APS25608N PSRAM on OSPI bus with memory mapped mode. The MCU run at 1.8V, 160MHz system clock. Previously, I used APS12808N at 80MHz and 3.3V VDD without any issues.
Currently, the PSRAMs run at 50MHz, but need to speed up to 100 or 160MHz.
I thought the aps256's default settings should be good up to 100MHz, but they weren't.
My working settings at 50MHz was ( relevant source in attachment):
MR0: Fix type latency, latency code 5, and full strength (25 ohms).
MR8: 32Byte Warp burst and without crossing.
OSPI settings are:
Dummy cycles: Read = 8, Write = 4
hospi->Init.FifoThreshold = 4;
hospi->Init.DualQuad = HAL_OSPI_DUALQUAD_DISABLE;
hospi->Init.MemoryType = HAL_OSPI_MEMTYPE_APMEMORY;
hospi->Init.DeviceSize = 25;
hospi->Init.ChipSelectHighTime = 2;
hospi->Init.FreeRunningClock = HAL_OSPI_FREERUNCLK_DISABLE;
hospi->Init.ClockMode = HAL_OSPI_CLOCK_MODE_0;
hospi->Init.WrapSize = HAL_OSPI_WRAP_NOT_SUPPORTED;
hospi->Init.ClockPrescaler = 2;
hospi->Init.SampleShifting = HAL_OSPI_SAMPLE_SHIFTING_NONE; // None
hospi->Init.DelayHoldQuarterCycle = HAL_OSPI_DHQC_ENABLE;
hospi->Init.ChipSelectBoundary = 10;
hospi->Init.DelayBlockBypass = HAL_OSPI_DELAY_BLOCK_USED;
hospi->Init.MaxTran = 0;
hospi->Init.Refresh = 640;
So, I try to speed up to 80MHz:
The MR0 and MR8 register settings are same, and it written MRs to APS256 successfully (I read back and compared ).
For the best delay block settings, I ran the delay block fine tuner, but doesn't found any good option.
I also tried to modify MR0 values ( increase / decrease the latency code, changed the drive strength, etc.), without any success.
I played with the refresh time used calculated values. I wrote a simple delay block tuner like function to search a good refresh time.
I measured the clock, chip select and data0 lines against with oscilloscope, and I saw only a little overshoot, but the timings was good. (fast signal rising and falling, and data lines stabilized on time)
I think, it's only a configuration or settings-related issue.
At the end, I confused, what is the relationship between latency code and dummy cycle.
What is the best settings: How can I speed up to 100 or 160MHz the PSRAMs?
Please check my attached code.
Thank you.