CCS/PROCESSOR-SDK-AM437X: Writing to flash with 4 byte addresses in Memory Map mode. TI AM437x

Tool/software: Code Composer Studio

This is regarding the Sitara AM437x industrial development kit.

Reading the AM437x ARM Cortext -A9 Processors Technical Reference Manual: Page 3693

• In order to be able to utilize 4 byte address mode, you must change the QSPI_SETUP_REG_0 field NUM_A_BYTES bits 9-8.
  • You must change this default value 0x20203 to 0x20303. 
    • 

Following this information, upon the start of my program (This could be considered in main), I do all the initialization. The highlighted line is where I change the register value.

Before my register call:

/* Init SPI driver */
SPI_init();

/* Default SPI configuration parameters */
SPI_Params_init(&spiParams);

if(m_flashHandle == 0)
{
   /* Open QSPI driver */
   m_flashHandle = SF25FL_open(((QSPI_INSTANCE - 1)+(QSPI_OFFSET)), &spiParams);

   /* Get Hardware attributes */
   m_spiHandle = m_flashHandle->spiHandle;

   m_rxLines = QSPI_RX_LINES_QUAD;
   SPI_control(m_spiHandle, SPI_V1_CMD_SETRXLINES, (void *)&m_rxLines);

   m_hwAttrs = (QSPI_HwAttrs *) m_spiHandle->hwAttrs;

   /* Print flash Id */
   FlashPrintId(m_flashHandle);
}

if(QSPI_RX_LINES_QUAD == m_hwAttrs->rxLines)
{
   S25FLFlash_QuadModeEnable(m_flashHandle);
}

QSPI_REG(QSPI_REG_0) = FOUR_BYTE_ENABLE;

After my Register change call:

This is showing that on the Sitara board, 4 byte addressing mode is now enabled.

From here I enter into SF25FL_bufferWrite() in S25FL.c:

up until this point the register still reads the required: 00020303

Once I step past this instruction, the register changes too:

This change in the register changed the value to a write command sending only 3 address bytes.

The problem with this is that this part of code is a loop, and so for all of the loop is sending three address bytes.

Any insight on how to get 4 byte address mode working with MMAP mode would be greatly appreciated.