Split home bank

1 files changed, 92 insertions, 0 deletions

diff --git a/src/home/farcall.asm b/src/home/farcall.asm
new file mode 100644
index 0000000..8474ca9
--- /dev/null
+++ b/src/home/farcall.asm
@@ -0,0 +1,92 @@
+; RST18
+; this function affects the stack so that it returns to the pointer following
+; the rst call. similar to rst 28, except this always loads bank 1
+Bank1Call: ; 09ae (0:09ae)
+	push hl
+	push hl
+	push hl
+	push hl
+	push de
+	push af
+	ld hl, sp+$d
+	ld d, [hl]
+	dec hl
+	ld e, [hl]
+	dec hl
+	ld [hl], $0
+	dec hl
+	ldh a, [hBankROM]
+	ld [hld], a
+	ld [hl], HIGH(SwitchToBankAtSP)
+	dec hl
+	ld [hl], LOW(SwitchToBankAtSP)
+	dec hl
+	inc de
+	ld a, [de]
+	ld [hld], a
+	dec de
+	ld a, [de]
+	ld [hl], a
+	ld a, $1
+;	fallthrough
+
+Bank1Call_FarCall_Common: ; 09ce (0:09ce)
+	call BankswitchROM
+	ld hl, sp+$d
+	inc de
+	inc de
+	ld [hl], d
+	dec hl
+	ld [hl], e
+	pop af
+	pop de
+	pop hl
+	ret
+
+; switch to the ROM bank at sp+4
+SwitchToBankAtSP: ; 9dc (0:9dc)
+	push af
+	push hl
+	ld hl, sp+$04
+	ld a, [hl]
+	call BankswitchROM
+	pop hl
+	pop af
+	inc sp
+	inc sp
+	ret
+
+; RST28
+; this function affects the stack so that it returns
+; to the three byte pointer following the rst call
+FarCall: ; 09e9 (0:09e9)
+	push hl
+	push hl
+	push hl
+	push hl
+	push de
+	push af
+	ld hl, sp+$d
+	ld d, [hl]
+	dec hl
+	ld e, [hl]
+	dec hl
+	ld [hl], $0
+	dec hl
+	ldh a, [hBankROM]
+	ld [hld], a
+	ld [hl], HIGH(SwitchToBankAtSP)
+	dec hl
+	ld [hl], LOW(SwitchToBankAtSP)
+	dec hl
+	inc de
+	inc de
+	ld a, [de]
+	ld [hld], a
+	dec de
+	ld a, [de]
+	ld [hl], a
+	dec de
+	ld a, [de]
+	inc de
+	jr Bank1Call_FarCall_Common