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TM4C129ENCPDT: Using part of flash memory to use as RAM

AKhilesh Gangwar
Intellectual 680 points
Part Number: TM4C129ENCPDT

Hi All,

I am using the tm4c129encpdt microcontroller with TI-RTOS. 

I have one major concern of memory-related. Most of the time my RAM usage is greater than 98% which makes us difficult to implement something new. Since we are in restrained memory environment, I was curious to know if somehow we can use the part of FLASH memory as the RAM. 

As per datasheet - https://www.ti.com/lit/ds/symlink/tm4c129encpdt.pdf?ts=1624026622136&ref_url=https%253A%252F%252Fwww.google.com%252F

Table 2-5, we can use FLASH as the data section too. 

I was trying this into tm4c129encpdt.cmd file-


SECTIONS
{
.intvecs: > 0x00000000
.text : > FLASH
.const : > FLASH
.cinit : > FLASH
.pinit : > FLASH
.init_array : > FLASH
 .data : > FLASH

.vtable : > SRAM
//.data : > SRAM

.bss : > SRAM
.sysmem : > SRAM
.stack : > SRAM
}

__STACK_TOP = __stack + 512;

If you see, I am trying to put the .data section into flash but it is not working. Even my code is not executing. I know RAM and FLASH are totally different but is there any way to use them this way?

Thanks

AkhiG

  • 0
    TI__Guru**** 191296 points

    Hi,

      You cannot use flash to replace RAM. The flash is a non-volatile memory. You cannot just write to it like writing a RAM. A change of value from 0 to 1 requires a erase to the flash. I will suggest you use the on-chip Emulated EEprom instead. There is 6kB of EEprom on chip. Please bear in mind the number of program/erase cycle the EEprom can support. It is spec'ed in the datasheet.

    uint32_t ui32EEPROMInit;
uint32_t pui32Data[2];
uint32_t pui32Read[2];
//
// Enable the EEPROM module.
//
SysCtlPeripheralEnable(SYSCTL_PERIPH_EEPROM0);
//
// Wait for the EEPROM module to be ready.
//
while(!SysCtlPeripheralReady(SYSCTL_PERIPH_EEPROM0))
{
}
//
// Wait for the EEPROM Initialization to complete
//
ui32EEPROMInit = EEPROMInit();
//
// Check if the EEPROM Initialization returned an error
// and inform the application
//
if(ui32EEPROMInit != EEPROM_INIT_OK)
{
while(1)
{
}
}
//
// Program some data into the EEPROM at address 0x400.
//
pui32Data[0] = 0x12345678;
pui32Data[1] = 0x56789abc;
EEPROMProgram(pui32Data, 0x400, sizeof(pui32Data));
//
// Read it back.
//
EEPROMRead(pui32Read, 0x400, sizeof(pui32Read));