Quad-SPI DDR indirect read mode dummy cycles count
Hello ST community,
I have some troubles with dummy cycles using Quad-SPI interface in DDR mode on STM32H743 and STM32F746.
I am trying to read data from IS25LP080D QSPI flash with FAST READ QUAD IO DTR MODE OPERATION (0xED command). It is 1-4-4 mode.
I am having trouble with number of dummy cycles. From IS25LP080D datasheet there must be 6 dummy sclk cycles between address and data. But to get 6 dummy cycles I must set cmd.DummyCycles = 3; in my program. Why there are 3 extra dummy cycles on diagram?
My read function for HAL is below. In this function I set cmd.DummyCycles = 3.
IS25LP_Status_t IS25LP_ReadQuadDDR(QSPI_HandleTypeDef *hqspi, uint8_t *buf, uint32_t addr, uint32_t size)
{
QSPI_CommandTypeDef cmd = {0};
cmd.InstructionMode = QSPI_INSTRUCTION_1_LINE;
cmd.Instruction = IS25LP_FAST_READ_QUAD_IO_DDR;
cmd.AddressMode = QSPI_ADDRESS_4_LINES;
cmd.AddressSize = QSPI_ADDRESS_24_BITS;
cmd.Address = addr;
cmd.AlternateByteMode = QSPI_ALTERNATE_BYTES_NONE;
cmd.AlternateBytesSize = QSPI_ALTERNATE_BYTES_24_BITS;
cmd.AlternateBytes = 0x0;
cmd.DummyCycles = 3;
cmd.DataMode = QSPI_DATA_4_LINES;
cmd.NbData = size;
cmd.DdrMode = QSPI_DDR_MODE_ENABLE;
cmd.DdrHoldHalfCycle = QSPI_DDR_HHC_HALF_CLK_DELAY;
cmd.SIOOMode = QSPI_SIOO_INST_EVERY_CMD;
if (HAL_QSPI_Command(hqspi, &cmd, QSPI_TIMEOUT) != HAL_OK) {
return IS25LP_ERROR;
}
if (HAL_QSPI_Receive(hqspi, buf, QSPI_TIMEOUT) != HAL_OK) {
return IS25LP_ERROR;
}
return IS25LP_OK;
}In my main.c I use this function to read 8 bytes of data:
status = IS25LP_ReadQuadDDR(&hqspi, readBuf, 0x1000, 8);And I am getting correct flash data:
First 8 bytes (DDR): 00 01 02 03 04 05 06 07
DCYC field in CCR register is 0x3, so there must be only 3 dummy cycles.
But on time diagram I can see 6 dummy cycles:
So I got 3 extra dummy cycles on STM32H743 board.
My question is: why there are extra dummy cycles? How should I calculate there number?
I also tried this code on STM32F746 board and I got 1 extra dummy cycles, but not 3.
Thank you for any thoughts!
I'm attaching my main.c and is25lp_mem.c for the reference.
Processor: STM32H743ZI
Board: Nucleo-H743ZI
Driver version: STM32Cube MCU Package for STM32H7 1.12.0
Compiler: GNU Tools for STM32 (12.3.rel1)
Cube MX 6.13.0