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+This article deals with a very sophisticated issue: programming the FlashROM. You will need thorough understanding of how the chip works. All of the code provided is commented well, but you still have to know what you are doing. You won't physically destroy your ROM chip or the cart, though.
+The code originates from my FMEEPROMPP utility. The ordinal numbers and byte codes refer to the FlashROM command sequence steps. PA and PD stand for the address and data to be programmed. All of this is explained in the FlashROM data sheet.
+Regarding flashing the chip, read especially the programming algorithm section and also see the waveform tables for timing information. This code appears to work, but especially the programming routine gets so complicated, there may be errors, so take care!
+You can find the print routine in [[base:string manipulation routines]].
+<code>
+; Retro Replay FlashROM operating routines by FMan/Tropyx
+; these are stripped-down example routines to program
+; data of arbitrary length at arbitrary ROM location,
+; and perform Block Erase and Chip Erase operations
+; WARNING! These routines, as they are presented here,
+; have not been tested! To use them, provide a main
+; program that does the initialization specified and
+; accommodate the given code to suit your needs, or better
+; yet: fully understand how it works and write your own!
+	BANK0 = 0
+	BANK1 = 8
+	BANK2 = $10
+	BANK3 = $18
+	BANK4 = $80
+	BANK5 = $88
+	BANK6 = $90
+	BANK7 = $98
+	SECCFG = $42	; $DE01 base value
+	A16BIT = $20	; value for A16 in $DE01
+	tempa = $80	; temporary variable definitions in
+	tempb = $81	; zero-page area used by BASIC and
+	tempc = $82	; free for us in an MC program
+	addrlo = $58	; beginning of data to flash
+	addrhi = $59
+	maxlo = $5a	; end address in C64's RAM
+	maxhi = $5b
+	secsel = $5e	; currently selected bank
+	srclo = $60	; used internally by the
+	srchi = $61	; programming routine
+	dstlo = $62
+	dsthi = $63
+	buflo = $64	; buffer used by the
+	bufhi = $65	; programming routine
+; subroutine that sends the beginning of a Command sequence
+RRCmd	sei			; note that this routines disales
+	lda #$13		; interrupts but does not enable
+	sta $de00		; them (operation is unfinished)
+	lda #$aa
+	sta $9555		; 1st: 555 - AA
+	ldx #$b
+	stx $de00
+	lsr
+	sta $8aaa		; 2nd: 2AA - 55
+	lda #$13
+	sta $de00
+	sty $9555		; 3rd: 555 - input reg Y
+	lda #3
+	sta $de00
+	rts
+; this is a table containing $DE01 values for all 16 ROM windows
+bank	!byte SECCFG+BANK0,SECCFG+BANK1,SECCFG+BANK2,SECCFG+BANK3
+	!byte SECCFG+BANK4,SECCFG+BANK5,SECCFG+BANK6,SECCFG+BANK7
+	!byte SECCFG+A16BIT+BANK0,SECCFG+A16BIT+BANK1,SECCFG+A16BIT+BANK2
+	!byte SECCFG+A16BIT+BANK3,SECCFG+A16BIT+BANK4,SECCFG+A16BIT+BANK5
+	!byte SECCFG+A16BIT+BANK6,SECCFG+A16BIT+BANK7
+; this routine will correctly handle wrapping over RR ROM banks
+; when address $A000 is reached, to program the FlashROM starting
+; from any address and proceeding to do so per custom length
+; before calling this routine, set addr and max accordingly,
+; set dsthi and dstlo to the starting address in the range of
+; $8000-$9FFF inside the currently selected ROM window, and
+; to select the correct ROM bank out of the 16 possible 8K
+; ones, preset the secsel variable that is used as an index
+; to the bank configuration value table above to select them
+Program	jsr RRReset		; reset the ROM for safety
+	lda addrlo		; copy starting address of data
+	sta srclo		; to program in the C64's RAM
+	lda addrhi
+	sta srchi
+	lda #11
+	sta $d011		; turn screen off
+	ldx secsel
+	lda bank,x
+	sta tempa		; current bank byte
+	stx tempc		; bank index
+	sei
+Progk	lda #$36		; switch BASIC off, to be able
+	sta 1			; to load data from RAM under it
+	ldy #0
+Progh	lda (srclo),y		; copy a pageful of data to the
+	sta (buflo),y		; buffer (initialize it to $600)
+	iny
+	bne Progh
+	lda #$37
+	sta 1
+Proga	ldy #$a0		; 3rd: 555 - A0
+	jsr RRCmd
+	lda tempa
+	sta $de01
+	ldy #0
+	lda (buflo),y
+	sta (dstlo),y		; 4th: PA - PD
+	and #$80
+	sta tempb		; store bit 7 for comparison
+Progb	lda (dstlo),y
+	tax
+	and #$80		; see if memory reads bit 7
+	cmp tempb
+	beq Progc		; Program operation finished
+	txa
+	and #$20		; check error bit
+	beq Progb
+	lda #0
+	sta $de00
+	cli
+	lda #<errstr
+	sta dst
+	lda #>errstr
+	bne Progd		; unconditional - error msg
+Progc	lda srchi
+	cmp maxhi
+	bne Progj
+	lda buflo
+	cmp maxlo
+	beq Progf
+Progj	inc dstlo		; increment destination address
+	bne Proge
+	inc dsthi
+	lda dsthi
+	cmp #$a0
+	bne Proge
+	lda #$80		; next bank
+	sta dsthi
+	ldx tempc
+	inx
+	lda bank,x
+	sta tempa
+	stx tempc
+Proge	inc buflo		; increment source address
+	bne Proga
+	inc srchi
+	bne Progk		; unconditional
+Progf	lda #32
+	ldx #0
+Progg	sta $600,x		; clean up screen (buffer page)
+	inx
+	bne Progg
+Done	lda #0
+	sta $de00
+	cli
+	lda #<donestr		; print "Done"
+	sta dst
+	lda #>donestr
+Progd	sta dst+1
+	jsr print		; bring in this and dst definition
+	lda #27
+	sta $d011		; screen back on
+; this routine sends a Read/Reset command to the FlashROM
+RRReset	ldy #$f0		; 3rd: F0 - and this is enough
+	jsr RRCmd
+	lda #2			; set the cart to off state
+	sta $de00
+	cli
+	rts
+; this routine performs a Block Erase operation on one of the eight
+; 16K internal blocks of which the M29F010B chip's 128K is made
+; select a 8K ROM window that falls within the desired 16K region
+; to be erased - for example, if you have ROM bank 10 or 11 selected,
+; both will result in the ROM region $14000-17FFF to be erased
+; if you wish to change the operation of the routine so that
+; the secsel variable is interpreted to directly stand for the
+; 16K FlashROM block, uncomment the included asl instruction
+BErase	ldy #$80		; 3rd: 555 - 80
+	jsr RRCmd
+	ldx #SECCFG+BANK2
+	stx $de01
+	lda #$aa
+	sta $9555		; 4th: 555 - AA
+	ldy #SECCFG+BANK1
+	sty $de01
+	lsr
+	sta $8aaa		; 5th: 2AA - 55
+	lda secsel
+;	asl			; see note above
+	tax
+	lda bank,x		; set bank corresponding with
+	sta $de01		; currently selected ROM window
+	lda #$30
+	sta $8000		; 6th: BA - 30
+BErasea	ldx #80
+BErased	dex			; wait for a little while
+	bpl BErased
+BEraseb	lda $8000		; wait for Erase to finish
+	and #$a0
+	beq BEraseb
+	bmi Done
+BErasec	inc $d020		; chip failure
+	jmp BErasec
+; this routine performs Chip Erase - something discouraged by Jens,
+; but useful if you know you are going to be flashing the entire ROM
+CErase	ldy #$80		; 3rd: 555 - 80
+	jsr RRCmd
+	ldx #SECCFG+BANK2
+	stx $de01
+	lda #$aa
+	sta $9555		; 4th: 555 - AA
+	ldy #SECCFG+BANK1
+	sty $de01
+	lsr
+	sta $8aaa		; 5th: 2AA - 55
+	stx $de01
+	lda #$10
+	sta $9555		; 6th: 555 - 10
+	bne BErasea
+errstr	!pet 13,"programming error! aborted. ",0
+donestr	!pet 13,"done! ",0
+</code>