Where is the sram stored in memory in a stm32f411e-disco microcontroller?

 In the STM32F411E-DISCO microcontroller (based on the STM32F411VET6), the SRAM (Static RAM) is located in the memory map of the Cortex-M4 core. Here's a detailed breakdown:

---

STM32F411VET6 SRAM Memory Layout

The STM32F411 has 128 KB of SRAM, split into different regions:

SRAM Block	Address Range	Size	Purpose
SRAM1	0x2000 0000 - 0x2001 FFFF	112 KB	Main system RAM (fastest access)
SRAM2	0x2002 0000 - 0x2002 3FFF	16 KB	Secondary RAM (slower bus)

Key Notes:

1. SRAM1 (112 KB)

   • Primary RAM for data, stack, and heap.

   • Connected to the Cortex-M4 bus matrix for fast CPU/peripheral access.

2. SRAM2 (16 KB)

   • Can be used for additional data storage or DMA buffers.

   • Slightly slower access than SRAM1 (attached to a different bus).

---

Additional Memory Regions

• Flash Memory: 0x0800 0000 - 0x080F FFFF (512 KB, stores firmware).

• Peripherals: 0x4000 0000 - 0x5FFF FFFF (registers for GPIO, UART, etc.).

• Core Coupled Memory (CCM): Not present in STM32F411 (unlike STM32F4xx "CCM-RAM" models).

---

How to Verify SRAM in Code

You can check SRAM usage by analyzing the linker script (.ld file) or inspecting the compiler map file.
Example (STM32CubeIDE linker script snippet):

ld

MEMORY
{
  RAM (xrw)  : ORIGIN = 0x20000000, LENGTH = 112K
  RAM2 (xrw) : ORIGIN = 0x2001C000, LENGTH = 16K
}

---

Practical Implications

1. Stack/Heap Allocation: By default, the linker places these in SRAM1.

2. DMA Optimization: Use SRAM2 for DMA buffers to free up SRAM1.

3. Critical Data: Place frequently accessed variables in SRAM1 for speed.

---

Checking SRAM Usage at Runtime

Add this to your code to monitor free SRAM (crude method):

c

extern int _estack, _sheap; // Defined in linker script

void CheckFreeRAM() {
  int free_ram = (int)&_estack - (int)&_sheap;
  printf("Free SRAM: %d bytes\n", free_ram);
}

---

Summary

• SRAM1 (112 KB): Primary workspace (0x2000 0000).

• SRAM2 (16 KB): Auxiliary storage (0x2002 0000).

• No CCM-RAM in STM32F411.