diff --git a/ports/stm32/sdram.c b/ports/stm32/sdram.c
index e3500a121b..83b002dcff 100644
--- a/ports/stm32/sdram.c
+++ b/ports/stm32/sdram.c
@@ -180,14 +180,14 @@ static void sdram_init_seq(SDRAM_HandleTypeDef
     /* Step 6 : Configure a Auto-Refresh command */
     command->CommandMode           = FMC_SDRAM_CMD_AUTOREFRESH_MODE;
     command->CommandTarget         = FMC_SDRAM_CMD_TARGET_BANK;
-    command->AutoRefreshNumber     = 4;
+    command->AutoRefreshNumber     = MICROPY_HW_SDRAM_AUTOREFRESH_NUM;
     command->ModeRegisterDefinition = 0;
 
     /* Send the command */
     HAL_SDRAM_SendCommand(hsdram, command, 0x1000);
 
     /* Step 7: Program the external memory mode register */
-    tmpmrd = (uint32_t)SDRAM_MODEREG_BURST_LENGTH_2   |
+    tmpmrd = (uint32_t)FMC_INIT(SDRAM_MODEREG_BURST_LENGTH, MICROPY_HW_SDRAM_BURST_LENGTH) |
         SDRAM_MODEREG_BURST_TYPE_SEQUENTIAL   |
         FMC_INIT(SDRAM_MODEREG_CAS_LATENCY, MICROPY_HW_SDRAM_CAS_LATENCY) |
         SDRAM_MODEREG_OPERATING_MODE_STANDARD |
@@ -222,19 +222,18 @@ static void sdram_init_seq(SDRAM_HandleTypeDef
     /* Disable the MPU */
     HAL_MPU_Disable();
 
-    /* Configure the MPU attributes for SDRAM */
+    /* Configure the MPU attributes as Write-Through for External SDRAM */
     MPU_InitStruct.Enable = MPU_REGION_ENABLE;
     MPU_InitStruct.BaseAddress = SDRAM_START_ADDRESS;
-    MPU_InitStruct.Size = MPU_REGION_SIZE_4MB;
+    MPU_InitStruct.Size = MPU_REGION_SIZE_8MB;
     MPU_InitStruct.AccessPermission = MPU_REGION_FULL_ACCESS;
     MPU_InitStruct.IsBufferable = MPU_ACCESS_NOT_BUFFERABLE;
-    MPU_InitStruct.IsCacheable = MPU_ACCESS_NOT_CACHEABLE;
+    MPU_InitStruct.IsCacheable = MPU_ACCESS_CACHEABLE;
     MPU_InitStruct.IsShareable = MPU_ACCESS_NOT_SHAREABLE;
     MPU_InitStruct.Number = MPU_REGION_NUMBER0;
-    MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL1;
+    MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL0;
     MPU_InitStruct.SubRegionDisable = 0x00;
-    MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_DISABLE;
-
+    MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_ENABLE;
     HAL_MPU_ConfigRegion(&MPU_InitStruct);
 
     /* Enable the MPU */