Erasing the DFM

The DFM does not support the Erase Page operation. However, the DFM can be erased by writing 0xFF to all locations in the memory that need to be erased.
DFM Erase Routine

        CLRF    NVMADRL             ; Clear address low byte
        CLRF    NVMADRH             ; Clear address high byte
        MOVLW   0x31                ; DFM upper address
        MOVWF   NVMADRU             ; Set address upper byte

        SETF    NVMDATL             ; Load 0xFF to the data register
        BCF     INTCON0, GIE        ; Disable interrupts
        MOVLW   0x04                ; write with post increment command
        MOVWF   NVMCON1             
Loop:                               ; Loop to refresh array
; –––-- Required Sequence –––––––––––-
        MOVLW   0x55                ; Initiate unlock sequence
        MOVWF   NVMLOCK             
        MOVLW   0xAA                
        MOVWF   NVMLOCK             
        BSF     NVMCON0, GO         ; Set GO bit to begin write
; ––––––––––––––––––––––––––-–––––––––––-
        BTFSC   NVMCON0, GO         ; Wait for write to complete
        BRA     $-2

        MOVF    NVMADRL, F          ; test address low byte
        BTFSS   STATUS,Z            
        BRA     Loop                ; Not zero, do it again
; The following 4 lines of code are not needed if DFM is 256 bytes or less
        MOVLW   0x03                ; Move 0x03 to working register
        CPFSGT  NVMADRH             ; Compare address high byte with working register

        BRA     Loop                ; Skip when high address exceeds DFM range
                                    ; Else go back to erase loop
        CLRF    NVMCON1             ; Disable writes
        BSF     INTCON0, GIE        ; Enable interrupts