1 files changed, 43 insertions, 0 deletions
diff --git a/src/home/hblank.asm b/src/home/hblank.asm
new file mode 100644
index 0000000..acf2eaa
--- /dev/null
+++ b/src/home/hblank.asm
@@ -0,0 +1,43 @@
+; copy b bytes of data from hl to de, but only during hblank
+HblankCopyDataHLtoDE:
+	push bc
+.loop
+	ei
+	di
+	ldh a, [rSTAT]       ;
+	and STAT_LCDC_STATUS ;
+	jr nz, .loop         ; assert hblank
+	ld a, [hl]
+	ld [de], a
+	ldh a, [rSTAT]       ;
+	and STAT_LCDC_STATUS ;
+	jr nz, .loop         ; assert still in hblank
+	ei
+	inc hl
+	inc de
+	dec b
+	jr nz, .loop
+	pop bc
+	ret
+
+; copy c bytes of data from de to hl, but only during hblank
+HblankCopyDataDEtoHL:
+	push bc
+.loop
+	ei
+	di
+	ldh a, [rSTAT]       ;
+	and STAT_LCDC_STATUS ;
+	jr nz, .loop         ; assert hblank
+	ld a, [de]
+	ld [hl], a
+	ldh a, [rSTAT]       ;
+	and STAT_LCDC_STATUS ;
+	jr nz, .loop         ; assert still in hblank
+	ei
+	inc hl
+	inc de
+	dec c
+	jr nz, .loop
+	pop bc
+	ret