Hello,
I'm using STM32H75x and NOR flash e.g. IS29GL064. I get the NOR demo running but I'd like to do modifications in order to get rid of all the polling stuff.
According to the demo, the FMC is configured like this
hnor1.Init.NSBank = FMC_NORSRAM_BANK3;
hnor1.Init.DataAddressMux = FMC_DATA_ADDRESS_MUX_DISABLE;
hnor1.Init.MemoryType = FMC_MEMORY_TYPE_NOR;
hnor1.Init.MemoryDataWidth = FMC_NORSRAM_MEM_BUS_WIDTH_16;
hnor1.Init.BurstAccessMode = FMC_BURST_ACCESS_MODE_DISABLE;
hnor1.Init.WaitSignalPolarity = FMC_WAIT_SIGNAL_POLARITY_LOW;
hnor1.Init.WaitSignalActive = FMC_WAIT_TIMING_BEFORE_WS;
hnor1.Init.WriteOperation = FMC_WRITE_OPERATION_ENABLE;
hnor1.Init.WaitSignal = FMC_WAIT_SIGNAL_ENABLE;
hnor1.Init.ExtendedMode = FMC_EXTENDED_MODE_DISABLE;
hnor1.Init.AsynchronousWait = FMC_ASYNCHRONOUS_WAIT_ENABLE;
hnor1.Init.WriteBurst = FMC_WRITE_BURST_DISABLE;
hnor1.Init.ContinuousClock = FMC_CONTINUOUS_CLOCK_SYNC_ASYNC;
hnor1.Init.WriteFifo = FMC_WRITE_FIFO_ENABLE;
hnor1.Init.PageSize = FMC_PAGE_SIZE_NONE;I wonder here about the "FMC_ASYNCHRONOUS_WAIT_ENABLE". I can remember that there are pretty old µC out which are waiting for a slow memory to get ready by using a wait signal. While memory is busy the µC is stalled and is inserting wait states. RM0433 seems to implicate this
According to the IS29GL064 datasheet, the flash seems not to make use of the RD/BSY (connected to FMC_NWAIT) signal during READ. Only during WRITE this signal tells the µC that it is busy programing data or that its receive buffer is full.
In the demo, all the WAIT timing seems to be handled in SW. In the demo the FMC_NWAIT pin is polled using HAL_NOR_GetStatus() after each single HAL_NOR_Program() call or after HAL_NOR_ProgramBuffer(). I think it would make sense to use IRQ fired by FMC_NWAIT instead of polling the pin.
If so, can I change the configuration to FMC_ASYNCHRONOUS_WAIT_DISABLE or does this have any drawback? Is there any recent asynchronous NOR flash that is using the NWAIT pin during READ/WRITE cycle and which must be handled by the FMC in hardware?
In the demo all data is written word by word. What about using DMA, does the NWAIT signal probably synchronize the flash data transfer with the DMA?
Thank you.
