MSP-EXP430FR5994: SD card not working when .bss section moved to FRAM

Hello Soumyajit,

the first thing to look into would be the functions you're using for the SD card functionality, which now instead of RAM, should deal with FRAM. While FRAM can be used for purposes like RAM, there are still differences, especially in respect of the available addressing modes. So in many cases functions, which have been using variables in RAM cannot be ported to FRAM functionality without respective changes.

Please see our documentation for further details.

Unfortunately for the FR5994 and other FR5xx/6xx derivatives, we have no assembler examples, but for the FRAM functionality, you can use also FR2xx examples, like this one:

; --COPYRIGHT--,BSD_EX
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;  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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;  OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
;  EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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; ******************************************************************************
;
;                        MSP430 CODE EXAMPLE DISCLAIMER
;
;  MSP430 code examples are self-contained low-level programs that typically
;  demonstrate a single peripheral function or device feature in a highly
;  concise manner. For this the code may rely on the device's power-on default
;  register values and settings such as the clock configuration and care must
;  be taken when combining code from several examples to avoid potential side
;  effects. Also see www.ti.com/grace for a GUI- and www.ti.com/msp430ware
;  for an API functional library-approach to peripheral configuration.
;
; --/COPYRIGHT--
;******************************************************************************
;   MSP430FR211x Demo - Long word writes to FRAM
;
;   Description: Use long word write to write to 512 byte blocks of FRAM.
;   Toggle LED after every 100 writes.
;   NOTE: Running this example for extended periods will impact the FRAM
;   endurance.
;   ACLK = REFO, MCLK = SMCLK = default DCODIV = ~1MHz
;
;           MSP430FR2111
;         ---------------
;     /|\|               |
;      | |               |
;      --|RST            |
;        |               |
;        |          P1.0 |---> LED
;
;   Xiaodong Li
;   Texas Instruments Inc.
;   Dec. 2015
;   Built with Code Composer Studio v6.1
;******************************************************************************
            .cdecls C,LIST,"msp430.h"  ; Include device header file
            
FRAM_write_ptr     .set    R5
data               .set    R6
count              .set    R7
FRAM_TEST_START    .set    0xFD00

;-------------------------------------------------------------------------------
            .def    RESET                   ; Export program entry-point to
                                            ; make it known to linker.
;-------------------------------------------------------------------------------

            .text                           ; Assemble to Flash memory
            .retain                         ; Ensure current section gets linked
            .retainrefs

RESET       mov.w   #__STACK_END,SP         ; Initialize stack pointer
StopWDT     mov.w   #WDTPW+WDTHOLD,&WDTCTL  ; Stop WDT

            bis.b    #01h,&P1DIR
            bic.w    #LOCKLPM5,PM5CTL0      ; Unlock I/O pins

            mov.w    #1111h,data            ; Initialize dummy data
            mov.w    #00h,count             ; Initialize counter

Mainloop    inc.w    data
            mov.w    #FRAM_TEST_START,FRAM_write_ptr
            call    #FRAMWrite                ; Endless loop
            inc.w    count                    ; Use R14 as counter
            cmp.w    #101,count
            jnz        Mainloop
            xor.b    #01h,&P1OUT                ; Toggle LED to show 512 bytes
            clr.w    count                    ; ...have been written
            mov.w    #0x1111,data            ; After 100 times, reset dummy data
            jmp        Mainloop

;------------------------------------------------------------------------------
FRAMWrite     ; Write to the FRAM
;------------------------------------------------------------------------------
            clr.w    R15                        ; Use gen purpose register as index
Start       inc.w    R15
            mov.w    #FRWPPW,SYSCFG0
            cmp.w    #101h,R15                ; for 128 blocks...
            jhs      Exit
            mov.w    data,0x0(FRAM_write_ptr) ; write to FRAM
            incd.w   FRAM_write_ptr
            jmp      Start
            mov.w    #FRWPPW+PFWP,SYSCFG0
Exit        ret
;-------------------------------------------------------------------------------
; Stack Pointer definition
;-------------------------------------------------------------------------------
            .global __STACK_END
            .sect   .stack
            
;-------------------------------------------------------------------------------
; Interrupt Vectors
;-------------------------------------------------------------------------------
            .sect   ".reset"                ; MSP430 RESET Vector
            .short  RESET
            .end

Best regards

Peter