1 files changed, 55 insertions, 0 deletions
diff --git a/engine/bcd.asm b/engine/bcd.asm
new file mode 100755
index 0000000..53f0b20
--- /dev/null
+++ b/engine/bcd.asm
@@ -0,0 +1,55 @@
+INCLUDE "constants.asm"
+	
+SECTION "BCD", ROMX[$4de3], BANK[$03]
+
+AddBCD: ; 03:4de3
+	and a
+	ld b, c
+.add
+	ld a, [de]
+	adc [hl]
+	daa
+	ld [de], a
+	dec de
+	dec hl
+	dec c
+	jr nz, .add
+	jr nc, .done
+	
+	ld a, $99
+	inc de
+	
+.fill
+	ld [de], a
+	inc de
+	dec b
+	jr nz, .fill
+
+.done
+	ret
+
+
+SubBCD: ; 03:4df9
+	and a
+	ld b, c
+.sub
+	ld a, [de]
+	sbc [hl]
+	daa
+	ld [de], a
+	dec de
+	dec hl
+	dec c
+	jr nz, .sub
+	jr nc, .done
+	ld a, 0
+	inc de
+	
+.fill
+	ld [de], a
+	inc de
+	dec b
+	jr nz, .fill
+	scf
+.done
+	ret
+\ No newline at end of file