Use SDCC's new calling convention

(this is an ABI breaking change, and will require changes to
user-written asm functions or their declarations)

33 files changed, 156 insertions, 199 deletions

diff --git a/CHANGES.md b/CHANGES.md
index dd8d30b..9859d11 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,11 @@
+## Release 1.2.0 - 2022-??-??
+
+ - Support for the new SDCC calling convention (SDCC 4.2.0 or later)
+ - Small fixes in the build scripts
+
+ For older versions of SDCC (or the old calling convention), please
+ use version 1.1.14.
+
 ## Release 1.1.14 - 2023-06-17
 
  - Small improvements in the API, around const parameters
diff --git a/README.md b/README.md
index 500109e..c79fd25 100644
--- a/README.md
+++ b/README.md
@@ -22,15 +22,19 @@ deep knowledge of the system.
  - GNU Make (others may work)
  - a POSIX compatible environment
 
-The [SDCC](http://sdcc.sourceforge.net/) compiler is also needed. Check the
-following table for some hints on compatibility.
+The [SDCC](http://sdcc.sourceforge.net/) compiler is also needed, version 4.2.0
+or later (using the new calling convention).
+
+Check the following table for some hints on compatibility.
 
 | Version | Compatible | Comments                                                |
 | ---     | ---        | ---                                                     |
-| 3.9.0   | yes        | -                                                       |
-| 4.0.0   | yes        | -                                                       |
-| 4.1.0   | no         | At least on Linux amd64 it generates broken Z80 code    |
-| 4.2.0   | yes        | Needs option in `config.env`, edit the file for details |
+| 4.2.0   | yes        | -                                                       |
+| 4.3.0   | ?          | Untested                                                |
+| 4.4.0   | no         | Generates broken Z80 code                               |
+
+To use an older version of SDCC (or the old calling convention), ubox MSX lib
+1.1.14 is the latest supported version.
 
 If you want to build the example you will also need:
 
diff --git a/config.env b/config.env
index 3cdc92c..32c6bb3 100644
--- a/config.env
+++ b/config.env
@@ -3,5 +3,5 @@
 # Size of the resulting ROM
 ROM_MAX=0x8000
 
-# uncomment for sdcc 4.2.0 or later
-#EXTRA_CFLAGS += --sdcccall 0
+# To add extra flags
+#EXTRA_CFLAGS += ???
diff --git a/game/src/helpers.c b/game/src/helpers.c
index 9aa4785..295c504 100644
--- a/game/src/helpers.c
+++ b/game/src/helpers.c
@@ -7,7 +7,7 @@
 /**
  * Put a zero terminated string on the screen using tiles.
  *
- * The font starts on the tileset on tile 128 and the fist char in our has
+ * The font starts on the tileset on tile 128 and the fist char in our font has
  * ASCII value 31, so it is adjusted so we can use ASCII *uppercase* directly
  * in our C code.
  */
diff --git a/include/mplayer.h b/include/mplayer.h
index c13ac56..3ec66db 100644
--- a/include/mplayer.h
+++ b/include/mplayer.h
@@ -77,7 +77,7 @@ void mplayer_init(const uint8_t *song, uint8_t sub_song);
  * See [exporting songs and effects](#exporting-songs-and-effects) for details
  * on how to add effects to your project.
  */
-void mplayer_init_effects(const uint8_t *effects) __z88dk_fastcall;
+void mplayer_init_effects(const uint8_t *effects);
 
 // @Playback
 
@@ -170,12 +170,12 @@ void mplayer_play_effect_p(uint8_t effect_no, uint8_t chan, uint8_t inv_vol);
 /**
  * Stops the effect being played on `chan` channel.
  */
-void mplayer_stop_effect_channel(uint8_t chan) __z88dk_fastcall;
+void mplayer_stop_effect_channel(uint8_t chan);
 
 /**
  * Returns 0 if there's no sound effect being played on `chan` channel, or
  * a value different than 0 otherwise.
  */
-uint8_t mplayer_is_sound_effect_on(uint8_t chan) __z88dk_fastcall;
+uint8_t mplayer_is_sound_effect_on(uint8_t chan);
 
 #endif // _MPLAYER_H
diff --git a/include/ubox.h b/include/ubox.h
index fa56741..ed8f651 100644
--- a/include/ubox.h
+++ b/include/ubox.h
@@ -64,7 +64,7 @@
  * ubox_set_mode(2);
  * ```
  */
-void ubox_set_mode(uint8_t mode) __z88dk_fastcall;
+void ubox_set_mode(uint8_t mode);
 
 /**
  * Enables the screen.
@@ -193,7 +193,7 @@ uint8_t ubox_get_vsync_freq(void);
  * All the tiles functions use an index in this tile set (usually via a `tile`
  * parameter).
  */
-void ubox_set_tiles(const uint8_t *tiles) __z88dk_fastcall;
+void ubox_set_tiles(const uint8_t *tiles);
 
 /**
  * Sets the current color table for current tile set to the color table pointed
@@ -203,7 +203,7 @@ void ubox_set_tiles(const uint8_t *tiles) __z88dk_fastcall;
  * of the tiles table (8 rows, 8 bytes per tile). The colors will be loaded into
  * the VDP in all three screen sections.
  */
-void ubox_set_tiles_colors(const uint8_t *colors) __z88dk_fastcall;
+void ubox_set_tiles_colors(const uint8_t *colors);
 
 /**
  * Puts a tile from current tile set on the screen. The tile is identified by
@@ -246,7 +246,7 @@ uint8_t ubox_get_tile(uint8_t x, uint8_t y);
  * See [ubox_set_tiles](#ubox_set_tiles) for for information on how to set a
  * tile set.
  */
-void ubox_fill_screen(uint8_t tile) __z88dk_fastcall;
+void ubox_fill_screen(uint8_t tile);
 
 // @Interrupt and clock functions
 
@@ -286,7 +286,7 @@ void ubox_fill_screen(uint8_t tile) __z88dk_fastcall;
  * are disabled, and because of that some BIOS functions, such as `CHGET`,
  * won't work.
  */
-void ubox_init_isr(uint8_t wait_ticks) __z88dk_fastcall;
+void ubox_init_isr(uint8_t wait_ticks);
 
 /**
  * Installs a user interrupt handler.
@@ -311,7 +311,7 @@ void ubox_init_isr(uint8_t wait_ticks) __z88dk_fastcall;
  * ubox_set_user_isr(my_isr);
  * ```
  */
-void ubox_set_user_isr(void (*fn)(void)) __z88dk_fastcall;
+void ubox_set_user_isr(void (*fn)(void));
 
 /**
  * Waits for a maximum `wait_ticks` interrupts (see [ubox_init_isr](#ubox_init_isr)).
@@ -364,7 +364,7 @@ void ubox_wait(void);
  * ubox_wait_for(250);
  * ```
  */
-void ubox_wait_for(uint8_t frames) __z88dk_fastcall;
+void ubox_wait_for(uint8_t frames);
 
 extern uint8_t ubox_tick;
 
@@ -519,7 +519,7 @@ uint8_t ubox_select_ctl(void);
  * }
  * ```
  */
-uint8_t ubox_read_ctl(uint8_t control) __z88dk_fastcall;
+uint8_t ubox_read_ctl(uint8_t control);
 
 #define UBOX_MSX_CTL_CURSOR  0
 #define UBOX_MSX_CTL_PORT1   1
@@ -554,7 +554,7 @@ uint8_t ubox_read_ctl(uint8_t control) __z88dk_fastcall;
  * }
  * ```
  */
-uint8_t ubox_read_keys(uint8_t row) __z88dk_fastcall;
+uint8_t ubox_read_keys(uint8_t row);
 
 // row 0
 #define UBOX_MSX_KEY_7           0x80
diff --git a/src/ap/ap.z80 b/src/ap/ap.z80
index b968853..882c75e 100644
--- a/src/ap/ap.z80
+++ b/src/ap/ap.z80
@@ -18,16 +18,7 @@
 .ez80
 
 _ap_uncompress::
-        ld hl, #2
-        add hl, sp
-        ld e, (hl)
-        inc hl
-        ld d, (hl)
-        inc hl
-        ld a, (hl)
-        inc hl
-        ld h, (hl)
-        ld l, a
+	ex de, hl
 
 ap_uncompress::
         ld ixl, #128
@@ -154,4 +145,3 @@ ap_getgammaloop:
         call ap_getbit
         jr c, ap_getgammaloop
         ret
-
diff --git a/src/mplayer/akm/akm_ubox.asm b/src/mplayer/akm/akm_ubox.asm
index cbbf8af..39aef74 100644
--- a/src/mplayer/akm/akm_ubox.asm
+++ b/src/mplayer/akm/akm_ubox.asm
@@ -7,11 +7,10 @@ PLY_AKM_ROM_Buffer = #c000
 
 include "PlayerAkm.asm"
 
-; IN: L = channel
+; IN: a = channel
 ; OUT: L = 0 if is not on
 PLY_AKM_IsSoundEffectOnDisarkGenerateExternalLabel:
 PLY_AKM_IsSoundEffectOn:
-	ld a,l
 	add a,a
 	add a,a
 	add a,a
@@ -22,6 +21,4 @@ PLY_AKM_IsSoundEffectOn:
 	ld a,(hl)
 	inc hl
 	or (hl)
-	ld l,a
 	ret
-
diff --git a/src/mplayer/mplayer_init.z80 b/src/mplayer/mplayer_init.z80
index 90b3824..ee922ca 100644
--- a/src/mplayer/mplayer_init.z80
+++ b/src/mplayer/mplayer_init.z80
@@ -5,13 +5,12 @@
 _mplayer_init::
 	ld ix, #2
 	add ix, sp
-
-	ld l, 0 (ix)
-	ld h, 1 (ix)
-	ld a, 2 (ix)
+	ld a, 0 (ix)
 
 	di
 	call _PLY_AKM_INIT
 	ei
 
-	ret
+	pop hl
+	inc sp
+	jp (hl)
diff --git a/src/mplayer/mplayer_play_effect.z80 b/src/mplayer/mplayer_play_effect.z80
index adf41b9..e2a233f 100644
--- a/src/mplayer/mplayer_play_effect.z80
+++ b/src/mplayer/mplayer_play_effect.z80
@@ -5,14 +5,13 @@
 .globl _PLY_AKM_PLAYSOUNDEFFECT
 
 _mplayer_play_effect::
-	ld hl, #2
-	add hl, sp
+	ld c, l
+	ld ix, #2
+	add ix, sp
+	ld b, 0 (ix)
 
-	ld a, (hl)
-	inc hl
-	ld c, (hl)
-	inc hl
-	ld b, (hl)
-
-        jp _PLY_AKM_PLAYSOUNDEFFECT
+	call _PLY_AKM_PLAYSOUNDEFFECT
 
+	pop hl
+	inc sp
+	jp (hl)
diff --git a/src/mplayer/mplayer_play_effect_p.z80 b/src/mplayer/mplayer_play_effect_p.z80
index 8efd705..9e428cd 100644
--- a/src/mplayer/mplayer_play_effect_p.z80
+++ b/src/mplayer/mplayer_play_effect_p.z80
@@ -7,39 +7,40 @@
 .globl _PLY_AKM_PLAYSOUNDEFFECT
 
 _mplayer_play_effect_p::
+	ld e, a
+	ld c, l
+
 	ld hl, #2
 	add hl, sp
+	ld b, (hl)
 
-	ld e, (hl)
-	inc hl
-	ld c, (hl)
-        inc hl
-        ld b, (hl)
-
-        ; e effect no
-        ; bc: channel and volume
-        push bc
-        push de
-        ld l, c
-        call _mplayer_is_sound_effect_on
+	; e effect no
+	; bc: channel and volume
+	push bc
+	push de
+	ld a, c
+	call _mplayer_is_sound_effect_on
 
-	ld a, l
 	or a
-        pop de
-        pop bc
+	pop de
+	pop bc
 	jr z, play_efx
 
 	ld a, (mplayer_current_efx)
-        ; comment out following line if you don't want to
-        ; replace current sound if is the same effect type
-        dec a
+	; comment out following line if you don't want to
+	; replace current sound if is the same effect type
+	dec a
 	cp e
-	ret nc
+	jp nc, play_exit
 
 play_efx:
 	; all good, play the effect
 	ld a, e
 	ld (mplayer_current_efx), a
 
-        jp _PLY_AKM_PLAYSOUNDEFFECT
+	call _PLY_AKM_PLAYSOUNDEFFECT
 
+play_exit:
+	pop hl
+	inc sp
+	jp (hl)
diff --git a/src/mplayer/mplayer_stop_effect_channel.z80 b/src/mplayer/mplayer_stop_effect_channel.z80
index 82eb5d7..2b03954 100644
--- a/src/mplayer/mplayer_stop_effect_channel.z80
+++ b/src/mplayer/mplayer_stop_effect_channel.z80
@@ -5,6 +5,4 @@
 .globl _PLY_AKM_STOPSOUNDEFFECTFROMCHANNEL
 
 _mplayer_stop_effect_channel::
-        ld a, l
         jp _PLY_AKM_STOPSOUNDEFFECTFROMCHANNEL
-
diff --git a/src/ubox/ubox_fill_screen.z80 b/src/ubox/ubox_fill_screen.z80
index e803f76..f07218c 100644
--- a/src/ubox/ubox_fill_screen.z80
+++ b/src/ubox/ubox_fill_screen.z80
@@ -4,8 +4,6 @@ FILVRM = 0x0056
 BG_TILE_MAP = 0x1800
 
 _ubox_fill_screen::
-	ld a, l
 	ld hl, #BG_TILE_MAP
 	ld bc, #768
 	jp FILVRM
-
diff --git a/src/ubox/ubox_get_tile.z80 b/src/ubox/ubox_get_tile.z80
index 3a6004d..9ea9b7b 100644
--- a/src/ubox/ubox_get_tile.z80
+++ b/src/ubox/ubox_get_tile.z80
@@ -4,13 +4,8 @@ RDVRM = 0x004a
 BG_TILE_MAP = 0x1800
 
 _ubox_get_tile::
-	ld hl, #2
-	add hl, sp
-
-	ld b, #0
-	ld c, (hl)
-	inc hl
-	ld l, (hl)
+	ld b, l
+	ld c, a
 
 	ld h, #0
 	add hl, hl
@@ -23,7 +18,4 @@ _ubox_get_tile::
 	ld bc, #BG_TILE_MAP
 	add hl, bc
 
-	call RDVRM
-	ld l, a
-	ret
-
+	jp RDVRM
diff --git a/src/ubox/ubox_get_vsync_freq.z80 b/src/ubox/ubox_get_vsync_freq.z80
index 681fe67..4a7f841 100644
--- a/src/ubox/ubox_get_vsync_freq.z80
+++ b/src/ubox/ubox_get_vsync_freq.z80
@@ -3,7 +3,6 @@
 _ubox_get_vsync_freq::
 	ld a, (#0x002b)
 	and #128
-	ld l, a
 	ret z
-	ld l, #1
+	ld a, #1
 	ret
diff --git a/src/ubox/ubox_isr.z80 b/src/ubox/ubox_isr.z80
index f25e35d..b8a19fe 100644
--- a/src/ubox/ubox_isr.z80
+++ b/src/ubox/ubox_isr.z80
@@ -12,7 +12,6 @@ REPCNT = 0xf3f7
 
 _ubox_init_isr::
 	di
-	ld a, l
 	ld (ubox_isr_wait_ticks), a
 	xor a
 	ld (ubox_isr_wait_tick), a
diff --git a/src/ubox/ubox_put_tile.z80 b/src/ubox/ubox_put_tile.z80
index 24e58b2..718027d 100644
--- a/src/ubox/ubox_put_tile.z80
+++ b/src/ubox/ubox_put_tile.z80
@@ -4,14 +4,11 @@ WRTVRM = 0x004d
 BG_TILE_MAP = 0x1800
 
 _ubox_put_tile::
+	ld c, a
+	ld b, l
+
 	ld hl, #2
 	add hl, sp
-
-	ld c, (hl)
-	inc hl
-	ld b, (hl)
-	inc hl
-
 	ld a, (hl)
 
 	ld h, #0
@@ -27,5 +24,8 @@ _ubox_put_tile::
 	ld bc, #BG_TILE_MAP
 	add hl, bc
 
-	jp WRTVRM
+	call WRTVRM
 
+	pop hl
+	inc sp
+	jp (hl)
diff --git a/src/ubox/ubox_read_ctl.z80 b/src/ubox/ubox_read_ctl.z80
index ae4fff9..d6f6a07 100644
--- a/src/ubox/ubox_read_ctl.z80
+++ b/src/ubox/ubox_read_ctl.z80
@@ -5,7 +5,6 @@ WRTPSG = 0x0093
 SNSMAT = 0x0141
 
 _ubox_read_ctl::
-	ld a, l
 	or a
 	jr z, is_keyb
 	dec a
@@ -13,7 +12,7 @@ _ubox_read_ctl::
 	dec a
 	jr z, is_joy2
 
-	ld l, #0
+	xor a
 	ret
 
 is_joy2:
@@ -49,7 +48,6 @@ call_psg:
 	xor a
 joy_extra_m:
 	or e
-	ld l, a
 	ret
 
 is_keyb:
@@ -96,5 +94,4 @@ is_keyb_dir:
 	or e
 	; added 2nd fire (M)
 
-	ld l, a
 	ret
diff --git a/src/ubox/ubox_read_keys.z80 b/src/ubox/ubox_read_keys.z80
index d32f2de..a8889fd 100644
--- a/src/ubox/ubox_read_keys.z80
+++ b/src/ubox/ubox_read_keys.z80
@@ -3,8 +3,6 @@
 SNSMAT = 0x0141
 
 _ubox_read_keys::
-	ld a, l
 	call SNSMAT
 	cpl
-	ld l, a
 	ret
diff --git a/src/ubox/ubox_read_vm.z80 b/src/ubox/ubox_read_vm.z80
index 7ef0f41..78df980 100644
--- a/src/ubox/ubox_read_vm.z80
+++ b/src/ubox/ubox_read_vm.z80
@@ -3,21 +3,23 @@
 LDIRMV = 0x0059
 
 _ubox_read_vm::
+	ex de, hl
+	; dst -> de
+	; len -> hl
+	ld c, l
+	ld b, h
+	; len -> bc
+
 	ld hl, #2
 	add hl, sp
-
-	ld e, (hl)
-	inc hl
-	ld d, (hl)
-	inc hl
-	ld c, (hl)
-	inc hl
-	ld b, (hl)
-	inc hl
 	ld a, (hl)
 	inc hl
 	ld h, (hl)
 	ld l, a
+	; src -> hl
 
-	jp LDIRMV
+	call LDIRMV
 
+	pop hl
+	pop bc
+	jp (hl)
diff --git a/src/ubox/ubox_select_ctl.z80 b/src/ubox/ubox_select_ctl.z80
index 9685bec..e313061 100644
--- a/src/ubox/ubox_select_ctl.z80
+++ b/src/ubox/ubox_select_ctl.z80
@@ -32,11 +32,11 @@ loop:
 	or a
 	jr nz, trigger_b
 
-	ld l, #0xff
+	ld a, #0xff
 	ret
 trigger_b:
 	dec b
 trigger:
 	dec b
-	ld l, b
+	ld a, b
 	ret
diff --git a/src/ubox/ubox_set_colors.z80 b/src/ubox/ubox_set_colors.z80
index 74a5b7f..4b89c99 100644
--- a/src/ubox/ubox_set_colors.z80
+++ b/src/ubox/ubox_set_colors.z80
@@ -6,17 +6,17 @@ BAKCLR = 0xf3ea
 BDRCLR = 0xf3eb
 
 _ubox_set_colors::
-	ld hl, #2
-	add hl, sp
-
-	ld a, (hl)
-	inc hl
 	ld (FORCLR), a
-	ld a, (hl)
-	inc hl
+	ld a, l
 	ld (BAKCLR), a
+
+	ld hl, #2
+	add hl, sp
 	ld a, (hl)
 	ld (BDRCLR), a
+
 	call CHGCLR
-	ret
 
+	pop hl
+	inc sp
+	jp (hl)
diff --git a/src/ubox/ubox_set_mode.z80 b/src/ubox/ubox_set_mode.z80
index 4635d34..373a145 100644
--- a/src/ubox/ubox_set_mode.z80
+++ b/src/ubox/ubox_set_mode.z80
@@ -3,6 +3,4 @@
 CHGMOD = 0x005f
 
 _ubox_set_mode::
-	ld a, l
 	jp CHGMOD
-
diff --git a/src/ubox/ubox_set_sprite_attr.z80 b/src/ubox/ubox_set_sprite_attr.z80
index 4e5c80e..ecf5952 100644
--- a/src/ubox/ubox_set_sprite_attr.z80
+++ b/src/ubox/ubox_set_sprite_attr.z80
@@ -4,14 +4,11 @@
 SP_ATTRS = 0x1b00
 
 _ubox_set_sprite_attr::
+	ld e, l
+	ld d, h
+
 	ld hl, #2
 	add hl, sp
-
-	ld e, (hl)
-	inc hl
-	ld d, (hl)
-	inc hl
-
 	ld l, (hl)
 	sla l
 	sla l
@@ -20,12 +17,11 @@ _ubox_set_sprite_attr::
 	add hl, bc
 
 	push de
-	ld bc, #4
-	push bc
-	push hl
+	ld de, #4
+	; hl: dst, de: len, stack: src
 	call _ubox_write_vm
-	pop af
-	pop af
-	pop af
-	ret
+
+	pop hl
+	inc sp
+	jp (hl)
 
diff --git a/src/ubox/ubox_set_sprite_pat16.z80 b/src/ubox/ubox_set_sprite_pat16.z80
index 59d7ccb..ee0f3c4 100644
--- a/src/ubox/ubox_set_sprite_pat16.z80
+++ b/src/ubox/ubox_set_sprite_pat16.z80
@@ -4,14 +4,11 @@
 SP_PATTERNS = 0x3800
 
 _ubox_set_sprite_pat16::
+	ld e, l
+	ld d, h
+
 	ld hl, #2
 	add hl, sp
-
-	ld e, (hl)
-	inc hl
-	ld d, (hl)
-	inc hl
-
 	ld l, (hl)
 	ld h, #0
 	add hl, hl
@@ -23,12 +20,10 @@ _ubox_set_sprite_pat16::
 	add hl, bc
 
 	push de
-	ld bc, #32
-	push bc
-	push hl
+	ld de, #32
+	; hl: dst, de: len, stack: src
 	call _ubox_write_vm
-	pop af
-	pop af
-	pop af
-	ret
 
+	pop hl
+	inc sp
+	jp (hl)
diff --git a/src/ubox/ubox_set_sprite_pat16_flip.z80 b/src/ubox/ubox_set_sprite_pat16_flip.z80
index 52f4ab7..7ac4077 100644
--- a/src/ubox/ubox_set_sprite_pat16_flip.z80
+++ b/src/ubox/ubox_set_sprite_pat16_flip.z80
@@ -4,14 +4,11 @@ WRTVRM = 0x004d
 SP_PATTERNS = 0x3800
 
 _ubox_set_sprite_pat16_flip::
+	ld e, l
+	ld d, h
+
 	ld hl, #2
 	add hl, sp
-
-	ld e, (hl)
-	inc hl
-	ld d, (hl)
-	inc hl
-
 	ld l, (hl)
 	ld h, #0
 	add hl, hl
@@ -32,7 +29,9 @@ _ubox_set_sprite_pat16_flip::
 	pop de
 	call flip
 
-	ret
+	pop hl
+	inc sp
+	jp (hl)
 
 flip:
 	ld b, #16
diff --git a/src/ubox/ubox_set_sprite_pat8.z80 b/src/ubox/ubox_set_sprite_pat8.z80
index 06b484c..c48588e 100644
--- a/src/ubox/ubox_set_sprite_pat8.z80
+++ b/src/ubox/ubox_set_sprite_pat8.z80
@@ -4,14 +4,11 @@
 SP_PATTERNS = 0x3800
 
 _ubox_set_sprite_pat8::
+	ld e, l
+	ld d, h
+
 	ld hl, #2
 	add hl, sp
-
-	ld e, (hl)
-	inc hl
-	ld d, (hl)
-	inc hl
-
 	ld l, (hl)
 	ld h, #0
 	add hl, hl
@@ -21,12 +18,10 @@ _ubox_set_sprite_pat8::
 	add hl, bc
 
 	push de
-	ld bc, #8
-	push bc
-	push hl
+	ld de, #8
+	; hl: dst, de: len, stack: src
 	call _ubox_write_vm
-	pop af
-	pop af
-	pop af
-	ret
 
+	pop hl
+	inc sp
+	jp (hl)
diff --git a/src/ubox/ubox_set_sprite_pat8_flip.z80 b/src/ubox/ubox_set_sprite_pat8_flip.z80
index b453253..64451e4 100644
--- a/src/ubox/ubox_set_sprite_pat8_flip.z80
+++ b/src/ubox/ubox_set_sprite_pat8_flip.z80
@@ -4,14 +4,11 @@ WRTVRM = 0x004d
 SP_PATTERNS = 0x3800
 
 _ubox_set_sprite_pat8_flip::
+	ld e, l
+	ld d, h
+
 	ld hl, #2
 	add hl, sp
-
-	ld e, (hl)
-	inc hl
-	ld d, (hl)
-	inc hl
-
 	ld l, (hl)
 	ld h, #0
 	add hl, hl
@@ -26,7 +23,10 @@ flip0:
 	inc hl
 	inc de
 	djnz flip0
-	ret
+
+	pop hl
+	inc sp
+	jp (hl)
 
 flip_and_copy:
 	ld a, (de)
diff --git a/src/ubox/ubox_set_tiles.z80 b/src/ubox/ubox_set_tiles.z80
index 7e4f42e..726eaae 100644
--- a/src/ubox/ubox_set_tiles.z80
+++ b/src/ubox/ubox_set_tiles.z80
@@ -19,4 +19,3 @@ _ubox_set_tiles::
 	ld de, #BG_TILES + #256 * 8 * 2
 	ld bc, #256 * 8
 	jp LDIRVM
-
diff --git a/src/ubox/ubox_set_tiles_colors.z80 b/src/ubox/ubox_set_tiles_colors.z80
index 4c4591b..6ca5d36 100644
--- a/src/ubox/ubox_set_tiles_colors.z80
+++ b/src/ubox/ubox_set_tiles_colors.z80
@@ -19,4 +19,3 @@ _ubox_set_tiles_colors::
 	ld de, #BG_COLS + 256  * 8 * 2
 	ld bc, #256 * 8
 	jp LDIRVM
-
diff --git a/src/ubox/ubox_wait_for.z80 b/src/ubox/ubox_wait_for.z80
index 5cc4649..f1984c8 100644
--- a/src/ubox/ubox_wait_for.z80
+++ b/src/ubox/ubox_wait_for.z80
@@ -4,11 +4,10 @@
 .globl ubox_isr_wait_tick
 
 _ubox_wait_for::
-	ld b, l
+	ld b, a
 wait_for_loop:
 	push bc
 	call _ubox_wait
 	pop bc
 	djnz wait_for_loop
 	ret
-
diff --git a/src/ubox/ubox_write_vm.z80 b/src/ubox/ubox_write_vm.z80
index 3d6606b..0daa7cc 100644
--- a/src/ubox/ubox_write_vm.z80
+++ b/src/ubox/ubox_write_vm.z80
@@ -3,21 +3,23 @@
 LDIRVM = 0x005c
 
 _ubox_write_vm::
+	ex de, hl
+	; dst -> de
+	; len -> hl
+	ld c, l
+	ld b, h
+	; len -> bc
+
 	ld hl, #2
 	add hl, sp
-
-	ld e, (hl)
-	inc hl
-	ld d, (hl)
-	inc hl
-	ld c, (hl)
-	inc hl
-	ld b, (hl)
-	inc hl
 	ld a, (hl)
 	inc hl
 	ld h, (hl)
 	ld l, a
+	; src -> hl
 
-	jp LDIRVM
+	call LDIRVM
 
+	pop hl
+	pop af
+	jp (hl)
diff --git a/src/ubox/ubox_wvdp.z80 b/src/ubox/ubox_wvdp.z80
index 90dfc86..b185f57 100644
--- a/src/ubox/ubox_wvdp.z80
+++ b/src/ubox/ubox_wvdp.z80
@@ -3,12 +3,6 @@
 WRITEVDP = 0x0047
 
 _ubox_wvdp::
-	ld hl, #2
-	add hl, sp
-
-	ld c, (hl)
-	inc hl
-	ld b, (hl)
-	call WRITEVDP
-	ret
-
+	ld c, a
+	ld b, l
+	jp WRITEVDP