STM32F469 with AS4C4M32S SDRAM only able to write first byte - stm32

Question

I have made a custom board that features a STM32F469NI MCU coupled with AS4C4M32S SDRAM.
Following are the SDRAM timing and register set information:
hsdram1.Instance = FMC_SDRAM_DEVICE;
/* hsdram1.Init */
hsdram1.Init.SDBank = FMC_SDRAM_BANK1;
hsdram1.Init.ColumnBitsNumber = FMC_SDRAM_COLUMN_BITS_NUM_8;
hsdram1.Init.RowBitsNumber = FMC_SDRAM_ROW_BITS_NUM_12;
hsdram1.Init.MemoryDataWidth = FMC_SDRAM_MEM_BUS_WIDTH_32;
hsdram1.Init.InternalBankNumber = FMC_SDRAM_INTERN_BANKS_NUM_4;
hsdram1.Init.CASLatency = FMC_SDRAM_CAS_LATENCY_3;
hsdram1.Init.WriteProtection = FMC_SDRAM_WRITE_PROTECTION_DISABLE;
hsdram1.Init.SDClockPeriod = FMC_SDRAM_CLOCK_PERIOD_2;
hsdram1.Init.ReadBurst = FMC_SDRAM_RBURST_DISABLE;
hsdram1.Init.ReadPipeDelay = FMC_SDRAM_RPIPE_DELAY_0;
/* SdramTiming */
SdramTiming.LoadToActiveDelay = 2;
SdramTiming.ExitSelfRefreshDelay = 7;
SdramTiming.SelfRefreshTime = 4;
SdramTiming.RowCycleDelay = 6;
SdramTiming.WriteRecoveryTime = 2;
SdramTiming.RPDelay = 2;
SdramTiming.RCDDelay = 2;
if (HAL_SDRAM_Init(&hsdram1, &SdramTiming) != HAL_OK)
{
Error_Handler( );
}
/* USER CODE BEGIN FMC_Init 2 */
FMC_SDRAM_CommandTypeDef cmd = { 0 };
cmd.CommandMode = FMC_SDRAM_CMD_CLK_ENABLE;
cmd.CommandTarget = FMC_SDRAM_CMD_TARGET_BANK1;
cmd.AutoRefreshNumber = 1;
cmd.ModeRegisterDefinition = 0;
HAL_SDRAM_SendCommand(&hsdram1, &cmd, 0xFFFF);
HAL_Delay(100);
cmd.CommandMode = FMC_SDRAM_CMD_PALL;
cmd.CommandTarget = FMC_SDRAM_CMD_TARGET_BANK1;
cmd.AutoRefreshNumber = 1;
cmd.ModeRegisterDefinition = 0;
HAL_SDRAM_SendCommand(&hsdram1, &cmd, 0xFFFF);
cmd.CommandMode = FMC_SDRAM_CMD_AUTOREFRESH_MODE;
cmd.CommandTarget = FMC_SDRAM_CMD_TARGET_BANK1;
cmd.AutoRefreshNumber = 8;
cmd.ModeRegisterDefinition = 0;
HAL_SDRAM_SendCommand(&hsdram1, &cmd, 0xFFFF);
cmd.CommandMode = FMC_SDRAM_CMD_LOAD_MODE;
cmd.CommandTarget = FMC_SDRAM_CMD_TARGET_BANK1;
cmd.AutoRefreshNumber = 1;
cmd.ModeRegisterDefinition = (uint32_t) 0x230; //also tried 0x231
HAL_SDRAM_SendCommand(&hsdram1, &cmd, 0xFFFF);
//Setup SDRAM Refresh Timer Register with the delay between refresh cycles of the SDRAM, this is SDRAM specific.
HAL_SDRAM_ProgramRefreshRate(&hsdram1, 1404); //Tried 1386
This same code works when running on a STM32F469-I DISCOVERY Board but fails when It is run on my custom carrier board.
On my board, whenever I write to any SDRAM address, only the first byte is READ/WRITTEN to, for example when I write 0x00 to address 0xC0000000, the data at that address when monitored under debugging contains 0x48129100 i.e first 3 BYTES are random garbage and only the last byte is written correctly(0x00), and suppose If i write 0xAA to the same address the data there when monitored contains the value 0x481291AA.
This is true to every address that I read/write to/from the external SDRAM.
Only the last byte is written/read.
The custom board schematic and PCB layout is identical to the STM32F469-I DISCO board.
Only difference is the RAM chip which instead of being MICRON one is Alliance Memory's AS4C4M32S .
What can be the issue of such a problem?

Answer 1

Reading SDRAM always uses at the full bit width, but writing requires to set the four signals BL0, BL1, BL2 and BL3 to say which bytes to write.
It sounds like only BL0 is currently working. Perhaps BL1-3 are not physically connected (hardware) or perhaps you just forgot to configure them (software).
(If it turns out to be a hardware problem then someone with the appropriate permissions will want to move this question and answer to the electronics stack exchange)