; CHARMAKER
; =========
; April 1986, Graham Harston
; Make a thicker Spectrum character set
;
; Part of Computer Studies 'O' level DefChar project
;

	ORG	#FF00		; Loadable to any address
START	PUSH	BC		; Get start address from the BC register and
	POP	DE		; decrease it by 768 to get the start of the
	DEC	D		; character set
	DEC	D
	DEC	D
	PUSH	DE
	LD	HL,15616	; Start of the character set in ROM
	LD	B,3		; Loop round for 3 sets of 256
LOOP1	LD	C,0		; Loop round 226 times
LOOP	LD	A,(HL)		; Get the byte from the ROM
	PUSH	BC		; Save the counters
	LD	B,A		; Put the byte in B
	ADD	A,A		; Shift A along one bit to the left
	OR	B		; Superimpose the original value
	LD	(DE),A		; and store in the RAM
	POP	BC		; Get the counters back
	INC	HL		; Increment the address pointers
	INC	DE
	DEC	C		; Decrement the first counter
	JR	NZ,LOOP		; Loop back if it's not zero
	DJNZ	LOOP1		; Decrement the second counter and loop back
	POP	DE		; Get the start of the character set back
	DEC	D		; Decrease by 256 to get the right value
	LD	(IY-3),D	; Store the high byte
	LD	(IY-4),E	; then the low byte in CHARS
	RET			; and return.

	DEFW	START,START