SDRAM STM32F429 FMC SDRAM DELAY

jacekborko · ‎2015-05-10

Posted on May 10, 2015 at 22:47

The original post was too long to process during our migration. Please click on the attachment to read the original post.

jijo137 · ‎2015-10-22

Posted on October 22, 2015 at 10:55

Hi Doopler,

I am also facing similar issue with the SDRAM. I am using STM32427IG. I have configured my system clock to 16 Mhz.

If you could solve the issue, Please tell me how it can be done

Thanks

waclawek.jan · ‎2015-10-22

Posted on October 22, 2015 at 12:16

Incorrect refresh rate? I don't use FMC with DRAMs but I'd be surprised if 16MHz clock would be enough.

JW

jijo137 · ‎2015-10-25

Posted on October 25, 2015 at 14:22

I have mentioned the SDRAM init code below.

void SDRAM_Init(void)

{

FMC_SDRAMInitTypeDef FMC_SDRAMInitStructure;

FMC_SDRAMTimingInitTypeDef FMC_SDRAMTimingInitStructure;

/* Enable FMC clock */

//rccEnableAHB3(RCC_AHB3ENR_FMCEN, FALSE);

RCC_AHB3PeriphClockCmd(RCC_AHB3ENR_FMCEN, ENABLE);

/* FMC Configuration ---------------------------------------------------------*/

/* FMC SDRAM Bank configuration */

/* TMRD: 2 Clock cycles */

FMC_SDRAMTimingInitStructure.FMC_LoadToActiveDelay =2;

/* TXSR: min=70ns 2x62ns (was 6x11.90ns) */

FMC_SDRAMTimingInitStructure.FMC_ExitSelfRefreshDelay =1;

/* TRAS: min=42ns 1x62ns (was 4x11.90ns) max=120k (ns) */

FMC_SDRAMTimingInitStructure.FMC_SelfRefreshTime =1;

/* TRC: min=63 2x62ns (was 6x11.90ns) */

FMC_SDRAMTimingInitStructure.FMC_RowCycleDelay =1;

/* TWR: 2 Clock cycles */

FMC_SDRAMTimingInitStructure.FMC_WriteRecoveryTime =2;

/* TRP: 15ns => 1x62ns ( was 2x11.90ns ) */

FMC_SDRAMTimingInitStructure.FMC_RPDelay =1;

/* TRCD: 15ns => 1x62ns (was 2x11.90ns) */

FMC_SDRAMTimingInitStructure.FMC_RCDDelay =1;

/* FMC SDRAM control configuration */

FMC_SDRAMInitStructure.FMC_Bank = FMC_Bank2_SDRAM;

/* Row addressing: [8..0] (was [7:0]) */

FMC_SDRAMInitStructure.FMC_ColumnBitsNumber = FMC_ColumnBits_Number_9b;

/* Column addressing: [12..0] (was [11:0]) */

FMC_SDRAMInitStructure.FMC_RowBitsNumber = FMC_RowBits_Number_13b;

FMC_SDRAMInitStructure.FMC_SDMemoryDataWidth = FMC_SDMemory_Width_16b;

FMC_SDRAMInitStructure.FMC_InternalBankNumber = FMC_InternalBank_Number_4;

FMC_SDRAMInitStructure.FMC_CASLatency = FMC_CAS_Latency_2;

FMC_SDRAMInitStructure.FMC_WriteProtection = FMC_Write_Protection_Disable;

FMC_SDRAMInitStructure.FMC_SDClockPeriod = FMC_SDClock_Period_2;

FMC_SDRAMInitStructure.FMC_ReadBurst = FMC_Read_Burst_Enable;

FMC_SDRAMInitStructure.FMC_ReadPipeDelay = FMC_ReadPipe_Delay_1;

FMC_SDRAMInitStructure.FMC_SDRAMTimingStruct = &FMC_SDRAMTimingInitStructure;

/* FMC SDRAM bank initialization */

FMC_SDRAMInit(&FMC_SDRAMInitStructure);

/* FMC SDRAM device initialization sequence */

SDRAM_InitSequence();

}

I have stored the data in address 0xD03AED64 is 0xD03AEE2C. I could read correctly when I tried continously. However, when I tried to read the data after some time I am getting the value 0x903AED64. My SDRAM is Micron MT48LC16M16A2. It works fine even in 8 Mhz frequency.

Thanks,

Gigo

waclawek.jan · ‎2015-10-25

Posted on October 25, 2015 at 18:33

> My SDRAM is Micron MT48LC16M16A2.

So what is its refresh period, and what is your refresh setting?

JW

jijo137 · ‎2015-10-26

Posted on October 26, 2015 at 08:29

The FMC clock is configured as half of SDCLK. ie. 8 Mhz (16mhz/2). So, an instruction takes 125 ns (1/8 Mhz) time. I have set the refresh rate to 125 ns. In the code snippet of previous post, it is given FMC_SDRAMTimingInitStructure.FMC_SelfRefreshTime =1; So, I hope it is suppose to refresh the storage at every 125 nano seconds.

When I have test the fmc clock with 16 Mhz, this is working fine. But when I reduced the fmc clock to 8 Mhz, I am getting this error

waclawek.jan · ‎2015-10-26

Posted on October 26, 2015 at 11:23

I suggest you to read thoroughly the SDRAM sub-chapter of the FMC chapter in RM and the memory's datasheet, concentrating on the refresh issues.

JW