IC:

RAM Layout Configuration Guide

Introduction

This chapter describes the default memory layout and provides guidance for customization.

RAM Memory Layout

Chipset integrates internal SRAM and expandable PSRAM with the following capacities:

Internal SRAM: 512KB
Expandable PSRAM: Available in various models with capacities including 0MB, 4MB, 8MB, and 16MB.

SRAM0 Layout (First 40KB)

The first 40KB of SRAM is reserved for storing ROM variables, BOOT code, and security processing functions, and this portion of memory is not accessible to users.

Items	Start address	Size	Description	Mandatory
KM0_ROM_BSS_RAM	0x2000_0000	4KB	KM0 ROM BSS	√
KM0_MSP_RAM	0x2000_1000	4KB	KM0 Main Stack Pointer	√
KM0_STDLIB_HEAP_NS	0x2000_2000	4KB	KM0 ROM STDLIB heap	√
KM4_MSP_NS	0x2000_3000	4KB	KM4 non-secure Main Stack Pointer	√
KM4_ROM_BSS_COMMON	0x2000_4000	3.25KB	KM4 ROM secure and non-secure common BSS	√
KM0_BOOT_RAM	0x2000_4D00	64B	KM0 IMG2 entry	√
KM0_IPC_RAM	0x2000_4E00	512B	Exchange messages between cores	√
KM4_ROM_BSS_NS	0x2000_5000	4KB	KM4 ROM non-secure common BSS	√
KM4_STDLIB_HEAP_NS	0x2000_6000	4KB	KM4 ROM non-secure STDLIB heap	√
KM4_ROM_BSS_S	0x3000_7000	4KB	KM4 ROM secure-only BSS	√
KM0_RTOS_STATIC_0_NS	0x2000_8000	4KB	KM0 RTOS static pool position	√
KM4_MSP_S	0x3000_9000	4KB	KM4 secure Main Stack Pointer	√

Item	Start address	Size	Description	Mandatory
KR4_ROM_BSS_RAM	0x2000_0000	4KB	KR4 ROM BSS	√
KR4_MSP_RAM	0x2000_1000	4KB	KR4 Main Stack Pointer	√
KR4_STDLIB_HEAP_NS	0x2000_2000	4KB	KR4 ROM STDLIB heap	√
KM4_MSP_NS	0x2000_3000	4KB	KM4 non-secure Main Stack Pointer	√
KM4_ROM_BSS_COMMON	0x2000_4000	2.25KB	KM4 ROM secure and non-secure common BSS	√
KR4_IPC_RAM	0x2000_4900	768B	Exchange messages between cores	√
KR4_BOOT_ENTRY_BACKUP	0x2000_4C00	64B	Backup KR4 IMG2 entry when SRAM1 is not used by KR4	√
KM4_ROM_BSS_NS	0x2000_5000	1.25KB	KM4 ROM non-secure common BSS	√
KR4_RAM_ONLY	0x2000_4C20	1KB	Used by power save flow when KR4 is NP	√
KM4_RAM_ONLY	0x2000_4E00	1KB	Used by power save flow when KM4 is NP	√
KM4_TIMER_IDLE_TASK_STACK	0x2000_6000	4KB	KM4 TIMER and IDLE task stack	√
KM4_ROM_BSS_S	0x3000_7000	4KB	KM4 ROM secure-only BSS	√
KM4_MSP_S	0x3000_8000	8KB	KM4 secure Main Stack Pointer	√

Item	Start address	Size	Description	Mandatory
KR4_ROM_BSS_RAM	0x2000_0000	4KB	KR4 ROM BSS	√
KR4_MSP_RAM	0x2000_1000	4KB	KR4 Main Stack Pointer	√
KR4_STDLIB_HEAP_NS	0x2000_2000	4KB	KR4 ROM STDLIB heap	√
KM4_MSP_NS	0x2000_3000	4KB	KM4 non-secure Main Stack Pointer	√
KM4_ROM_BSS_COMMON	0x2000_4000	2.25KB	KM4 ROM secure and non-secure common BSS	√
KR4_IPC_RAM	0x2000_4900	768B	Exchange messages between cores	√
KR4_BOOT_ENTRY_BACKUP	0x2000_4C00	64B	Backup KR4 IMG2 entry when SRAM1 is not used by KR4	√
KM4_ROM_BSS_NS	0x2000_5000	1.25KB	KM4 ROM non-secure common BSS	√
KR4_RAM_ONLY	0x2000_4C20	1KB	Used by power save flow when KR4 is NP	√
KM4_RAM_ONLY	0x2000_4E00	1KB	Used by power save flow when KM4 is NP	√
KM4_TIMER_IDLE_TASK_STACK	0x2000_6000	4KB	KM4 TIMER and IDLE task stack	√
KM4_ROM_BSS_S	0x3000_7000	4KB	KM4 ROM secure-only BSS	√
KM4_MSP_S	0x3000_8000	8KB	KM4 secure Main Stack Pointer	√

RAM & PSRAM Hybrid Layout

RAM layout With PSRAM

Item	Start address	Size (KB)	Description	Mandatory
SRAM0	0x2000_0000	40	For ROM BSS, MSP, …	√
KM4 Bootloader	0x3000_A000	24	KM4 secure bootloader, including code and data	√
KM4 BD RAM	0x2001_0000	352	KM4 BDRAM data, BSS and heap	√
KM0 BD RAM	0x2004_0000	96	KM0 BDRAM data, BSS and heap	√
KM4 PSRAM	0x6000_0000	3220	KM4 PSRAM code, can be empty	√
KM0 PSRAM	0x6032_5000	876	KM0 PSRAM code, can be empty	√
KM4 HEAP EXT	0x6FFF_FFFF	0	If KM4 heap is not enough, it can be used to extend the heap size	x
KM0 HEAP EXT	0x6FFF_FFFF	0	If KM0 heap is not enough, it can be used to extend the heap size	x

RAM layout With PSRAM

../../_images/ram_psram_layout_8726_lite.svg

Note

If RDP is not enabled, the KM4_BD_PSRAM_NSC/KM4_BD_PSRAM_ENTRY/KM4_BD_PSRAM_S are non-secure and would be merged into KM4_BD_PSRAM.

Item	Start address	Size	Description	Mandatory
SRAM0	0x2000_0000	40KB	For ROM BSS, MSP and so on	√
KM4 BOOTLOADER	0x2000_A000	24KB	For Bootloader	√
KM4 IMG3	0x6000_0000	64KB	KM4 IMG3, can be merged into KM4 PSRAM if IMG3 is not needed	√
KM4 PSRAM	0x6001_0000	1472KB	KM4 code, data, BSS and heap	√
KR4 PSRAM	0x6018_0000	1536KB	KR4 code, data, BSS and heap	√
DSP PSRAM	0x6030_0000	5120KB	DSP PSRAM	√
KM4 HEAP EXT	0x6FFF_FFFF	0	If KM4 Heap is not enough, it can be used to extend the heap size	x
KR4 HEAP EXT	0x6FFF_FFFF	0	If KR4 Heap is not enough, it can be used to extend the heap size	x

RAM layout With PSRAM

Note

If RDP is not enabled, the KM4_BD_PSRAM_NSC/KM4_BD_PSRAM_ENTRY/KM4_BD_PSRAM_S are non-secure and would be merged into KM4_BD_PSRAM.

Item	Start address	Size	Description	Mandatory
SRAM0	0x2000_0000	40KB	For ROM BSS, MSP …	√
KM4 BOOTLOADER	0x2000_A000	24KB	For Bootloader	√
KM4 BD RAM	0x2001_0000	352KB	KM4 BDRAM data, BSS and heap	√
KR4 BD RAM	0x2006_8000	96KB	KR4 BDRAM data, BSS and heap	√
KM4 IMG3	0x6000_0000	64KB	KM4 IMG3, can be merged into KM4 PSRAM if IMG3 is not needed	√
KM4 PSRAM	0x6001_0000	1472KB	KM4 code	√
KR4 PSRAM	0x6018_0000	1536KB	KR4 code	√
KM4 HEAP EXT	0x6FFF_FFFF	0	If KM4 Heap is not enough, it can be used to extend the heap size	x
KR4 HEAP EXT	0x6FFF_FFFF	0	If KR4 Heap is not enough, it can be used to extend the heap size	x

RAM layout Without PSRAM

Note

If RDP is not enabled, the KM4_BD_RAM_NSC/KM4_BD_RAM_ENTRY/KM4_BD_RAM_S are non-secure and would be merged into KM4_BD_PSRAM.

Item	Start address	Size	Description	Mandatory
SRAM0	0x2000_0000	40KB	For ROM BSS, MSP …	√
KM4 BOOTLOADER	0x2000_A000	24KB	For Bootloader	√
KM4 IMG3	0x2001_0000	64KB	KM4 IMG3, can be used by users if IMG3 is not needed	√
KM4 BD RAM	0x2002_0000	288KB	KM4 BDRAM data, BSS and heap	√
KR4 BD RAM	0x2006_8000	96KB	KR4 BDRAM data, BSS and heap	√

Bootloader Size Configuration

Bootloader Size Adjustment

When enlarging KM4_BOOT_RAM_S, ensure modified size is 4KB-aligned (MPC protection works in 4KB units).

Steps to modify bootloader size:

Configure CONFIG Link Option in menuconfig:
- SRAM selection sets KM4_BOOTLOADER_RAM_S to 24KB
- Flash selection sets KM4_BOOTLOADER_RAM_S to 4KB
Modify linker script parameter (path: {SDK}\amebaxxx_gcc_project\amebaxxx_layout.ld):
- Adjust KM4_IMG1_SIZE to change KM4_BOOTLOADER_RAM_S size
Rebuild project to generate new bootloader
If bootloader exceeds size limit:
- Update end address in km4_boot_all.bin
- Flash updated bootloader

Note

New bootloader version must be higher than current version for boot ROM loading

Bootloader Size Adjustment

When enlarging KM4_BOOT_RAM_S, ensure modified size is 4KB-aligned (MPC protection works in 4KB units).

Steps to modify bootloader size:

Configure CONFIG Link Option in menuconfig:
- SRAM selection sets KM4_BOOTLOADER_RAM_S to 24KB
- Flash selection sets KM4_BOOTLOADER_RAM_S to 4KB
Modify linker script parameter (path: {SDK}\amebaxxx_gcc_project\amebaxxx_layout.ld):
- Adjust KM4_IMG1_SIZE to change KM4_BOOTLOADER_RAM_S size
Rebuild project to generate new bootloader
If bootloader exceeds size limit:
- Update end address in km4_boot_all.bin
- Flash updated bootloader

Note

New bootloader version must be higher than current version for boot ROM loading

Bootloader Size Adjustment

When enlarging KM4_BOOT_RAM_S, ensure modified size is 4KB-aligned (MPC protection works in 4KB units).

Steps to modify bootloader size:

Configure CONFIG Link Option in menuconfig:
- SRAM selection sets KM4_BOOTLOADER_RAM_S to 24KB
- Flash selection sets KM4_BOOTLOADER_RAM_S to 4KB
Modify linker script parameter (path: {SDK}\amebaxxx_gcc_project\amebaxxx_layout.ld):
- Adjust KM4_IMG1_SIZE to change KM4_BOOTLOADER_RAM_S size
Rebuild project to generate new bootloader
If bootloader exceeds size limit:
- Update end address in km4_boot_all.bin
- Flash updated bootloader

Note

New bootloader version must be higher than current version for boot ROM loading

BD_RAM/BD_PSRAM Capacity Adjustment

BD_RAM Configuration

Steps to modify KM4 BD_RAM size:

Adjust KM4_BD_RAM end address by modifying RAM_KM0_IMG2_SIZE in:

{SDK}\amebadplus_gcc_project\amebaDplus_layout.ld
Rebuild and flash Bootloader with IMG2 OTA2 following APP OTA1 section

BD_PSRAM Configuration

To modify KM4 BD_PSRAM size:

First configure IMG2 execution position in menuconfig (select any PSRAM-related option)
Adjust KM4_BD_PSRAM end address by modifying PSRAM_KM4_IMG2_SIZE in:

{SDK}\amebadplus_gcc_project\amebaDplus_layout.ld

BD_RAM Configuration

Steps to modify KM4 BD_RAM size:

Configure IMG2 execution position in menuconfig (select any SRAM-related option):

Modify linker script parameters (path: {SDK}\amebalite_gcc_project\amebalite_layout.ld):

Adjust RAM_KM4_IMG2_SIZE or RAM_KR4_IMG2_SIZE
Update KM4_BD_RAM end address

/* IMG2 Size*/
#if defined(CONFIG_AP_CORE_KM4)
  #define RAM_KR4_IMG2_SIZE         KBYTES(96)
  #define KM4_IMG2_RAM_START        (KM4_RAM_TZ_SECURE_START + RAM_KM4_IMG3_SIZE)
  #define KR4_IMG2_RAM_START        (SRAM_END - RAM_KR4_IMG2_SIZE)
  #define RAM_KM4_IMG2_SIZE         (KR4_IMG2_RAM_START - KM4_IMG2_RAM_START)
#else
  #define RAM_KM4_IMG2_SIZE         KBYTES(96)
  #define KM4_IMG2_RAM_START        (KM4_RAM_TZ_SECURE_START + RAM_KM4_IMG3_SIZE)
  #define KR4_IMG2_RAM_START        (KM4_IMG2_RAM_START + RAM_KM4_IMG2_SIZE)
  #define RAM_KR4_IMG2_SIZE         (SRAM_END - KR4_IMG2_RAM_START)
#endif

Rebuild and flash Bootloader with IMG2 OTA2 following APP OTA1 section

BD_PSRAM Configuration

Steps to modify KM4 BD_PSRAM size:

Configure IMG2 execution position in menuconfig (select any PSRAM-related option)

Modify linker script parameters (path: {SDK}\amebalite_gcc_project\amebalite_layout.ld):

Adjust PSRAM_KM4_IMG2_SIZE
Update KM4_BD_PSRAM end address

#define PSRAM_KM4_IMG2_SIZE       (KBYTES(1536) - (PSRAM_TZ_NSC_SIZE + PSRAM_TZ_ENTRY_SIZE + PSRAM_KM4_IMG3_SIZE))
#define KM4_IMG2_PSRAM_START      (KM4_PSRAM_TZ_SECURE_START + PSRAM_KM4_IMG3_SIZE)
#define KR4_IMG2_PSRAM_START      (KM4_IMG2_PSRAM_START + PSRAM_KM4_IMG2_SIZE)
#define PSRAM_KR4_IMG2_SIZE       (PSRAM_DSP_START - KR4_IMG2_PSRAM_START)

BD_RAM Configuration

Steps to modify KM4 BD_RAM size:

Configure IMG2 execution position in menuconfig (select any SRAM-related option):

Modify linker script parameters (path: {SDK}\amebalite_gcc_project\amebalite_layout.ld):

Adjust RAM_KM4_IMG2_SIZE or RAM_KR4_IMG2_SIZE
Update KM4_BD_RAM end address

/* IMG2 Size*/
#if defined(CONFIG_AP_CORE_KM4)
  #define RAM_KR4_IMG2_SIZE         KBYTES(96)
  #define KM4_IMG2_RAM_START        (KM4_RAM_TZ_SECURE_START + RAM_KM4_IMG3_SIZE)
  #define KR4_IMG2_RAM_START        (SRAM_END - RAM_KR4_IMG2_SIZE)
  #define RAM_KM4_IMG2_SIZE         (KR4_IMG2_RAM_START - KM4_IMG2_RAM_START)
#else
  #define RAM_KM4_IMG2_SIZE         KBYTES(96)
  #define KM4_IMG2_RAM_START        (KM4_RAM_TZ_SECURE_START + RAM_KM4_IMG3_SIZE)
  #define KR4_IMG2_RAM_START        (KM4_IMG2_RAM_START + RAM_KM4_IMG2_SIZE)
  #define RAM_KR4_IMG2_SIZE         (SRAM_END - KR4_IMG2_RAM_START)
#endif

Rebuild and flash Bootloader with IMG2 OTA2 following APP OTA1 section

BD_PSRAM Configuration

Steps to modify KM4 BD_PSRAM size:

Configure IMG2 execution position in menuconfig (select any PSRAM-related option)

Modify linker script parameters (path: {SDK}\amebalite_gcc_project\amebalite_layout.ld):

Adjust PSRAM_KM4_IMG2_SIZE
Update KM4_BD_PSRAM end address

#define PSRAM_KM4_IMG2_SIZE       (KBYTES(1536) - (PSRAM_TZ_NSC_SIZE + PSRAM_TZ_ENTRY_SIZE + PSRAM_KM4_IMG3_SIZE))
#define KM4_IMG2_PSRAM_START      (KM4_PSRAM_TZ_SECURE_START + PSRAM_KM4_IMG3_SIZE)
#define KR4_IMG2_PSRAM_START      (KM4_IMG2_PSRAM_START + PSRAM_KM4_IMG2_SIZE)
#define PSRAM_KR4_IMG2_SIZE       (PSRAM_DSP_START - KR4_IMG2_PSRAM_START)

Heap Memory Configuration

System heap consists of multiple blocks initialized by os_heap_init() in component\os\freertos\freertos_heap5_config.c.

Initial PSRAM Heap Definition

PSRAM_HEAP1_START is invalid address
PSRAM_HEAP1_SIZE set to 0

Initial Heap Definition

KM4_PSRAM_HEAP_EXT (rwx) : ORIGIN = 0x6FFFFFFF, LENGTH = 0x6FFFFFFF - 0x6FFFFFFF  /* KM4 PSRAM Extended Heap */
KM0_PSRAM_HEAP_EXT (rwx) : ORIGIN = 0x6FFFFFFF, LENGTH = 0x6FFFFFFF - 0x6FFFFFFF  /* KM0 PSRAM Extended Heap */

KM4 Heap Extension

For insufficient KM4 heap:

Define unused PSRAM regions in linker script amebaDplus_layout.ld:
- Set valid Heap Start address
- Configure Heap Size value

Add heap blocks via system API:

bool os_heap_add(u8 *start_addr, size_t heap_size);

Rebuild and flash image to activate configuration

Note

Symbols defined in linker script (amebaDplus_layout.ld) must be declared in ameba_boot.h before usage

KM0 Heap Extension

For insufficient KM0 heap, modify KM0_PSRAM_HEAP_EXT parameter

Initial PSRAM Heap Definition

PSRAM_HEAP1_START is invalid address
PSRAM_HEAP1_SIZE set to 0

Initial Heap Definition

KM4_PSRAM_HEAP_EXT (rwx) : ORIGIN = 0x6FFFFFFF, LENGTH = 0x6FFFFFFF - 0x6FFFFFFF  /* KM4 PSRAM Extended Heap */
KR4_PSRAM_HEAP_EXT (rwx) : ORIGIN = 0x6FFFFFFF, LENGTH = 0x6FFFFFFF - 0x6FFFFFFF  /* KR4 PSRAM Extended Heap */

KM4 Heap Extension Procedure

When KM4 heap is insufficient:

Define unused PSRAM regions in linker script amebalite_layout.ld:
- Set valid Heap Start address
- Configure Heap Size value
Add heap blocks via system API:
```
bool os_heap_add(u8 *start_addr, size_t heap_size);
```
Note

Address must point to valid PSRAM space
Rebuild project and flash new image to activate extended heap

General Notes

Note

Symbols defined in linker script (amebalite_layout.ld) must be declared in ameba_boot.h
KR4 heap extension follows the same procedure

Initial PSRAM Heap Definition

PSRAM_HEAP1_START is invalid address
PSRAM_HEAP1_SIZE set to 0

Initial Heap Definition

KM4_PSRAM_HEAP_EXT (rwx) : ORIGIN = 0x6FFFFFFF, LENGTH = 0x6FFFFFFF - 0x6FFFFFFF  /* KM4 PSRAM Extended Heap */
KR4_PSRAM_HEAP_EXT (rwx) : ORIGIN = 0x6FFFFFFF, LENGTH = 0x6FFFFFFF - 0x6FFFFFFF  /* KR4 PSRAM Extended Heap */

KM4 Heap Extension Procedure

When KM4 heap is insufficient:

Define unused PSRAM regions in linker script amebalite_layout.ld:
- Set valid Heap Start address
- Configure Heap Size value
Add heap blocks via system API:
```
bool os_heap_add(u8 *start_addr, size_t heap_size);
```
Note

Address must point to valid PSRAM space
Rebuild project and flash new image to activate extended heap

General Notes

Note

Symbols defined in linker script (amebalite_layout.ld) must be declared in ameba_boot.h
KR4 heap extension follows the same procedure