MDF4K autostart: don't read controller at all

MDFourier 4K autostart is meant to behave as much like the NSF as
possible.

- Someone might make a dedicated cartridge of MDF4K for use on a
  disassembled console under repair with empty controller ports.
- I received an anecdotal report that at least one emulator
  developer implemented audio before input and NROM before NSF.
- Because some console models pass audio and controller signals
  through the same inverter amplifier, checking for the B Button
  during the test can be heard as buzzing.

The new sequence for autostart is as follows:

1. Show title screen for 1 second, to distinguish a bootup failure
   from muted audio.  There are concerns that this may not be long
   enough to get picky modern displays to synchronize to the signal.
2. Run the test and disregard input.
3. Show title screen until power off or reset.

Author: pinobatch

nes/makefile

@@ -25,8 +25,8 @@ objlist:=vwf7 zappertest overclock paldetect vwf_draw init \
 objlistnsf := mdfouriernsf mdfourier ntscPeriods
 objlistmdf4k := mdfourier4kfe mdfourier padsnodas ntscPeriods
 objlistmdf4kchr := mdfourier4kfe-chrrom mdfourier padsnodas ntscPeriods
-objlistmdf4kauto := mdfourier4kfe-autostart mdfourier padsnodas ntscPeriods
-objlistmdf4kchrauto := mdfourier4kfe-chrrom-autostart mdfourier padsnodas ntscPeriods
+objlistmdf4kauto := mdfourier4kfe-autostart mdfourier ntscPeriods
+objlistmdf4kchrauto := mdfourier4kfe-chrrom-autostart mdfourier ntscPeriods
 
 AS65:=ca65
 LD65:=ld65

nes/mdfourier4k-chrrom.cfg

@@ -23,7 +23,7 @@ SEGMENTS {
 
   INESHDR:    load = HEADER, type = ro, align = $10;
   DMC:        load = ROMF0, type = ro, align = 64, optional = yes;
-  LIBCODE:    load = ROMF0, type = ro;
+  LIBCODE:    load = ROMF0, type = ro, optional = yes;
   CODE:       load = ROMF0, type = ro, align = $20;
   RODATA:     load = ROMF0, type = ro;
 

nes/mdfourier4k.cfg

@@ -22,7 +22,7 @@ SEGMENTS {
 
   INESHDR:    load = HEADER, type = ro, align = $10;
   DMC:        load = ROMF0, type = ro, align = 64, optional = yes;
-  LIBCODE:    load = ROMF0, type = ro;
+  LIBCODE:    load = ROMF0, type = ro, optional = yes;
   CODE:       load = ROMF0, type = ro, align = $20;
   RODATA:     load = ROMF0, type = ro;
 

nes/src/mdfourier4kfe.s

@@ -23,6 +23,8 @@
 ; and can affect noise
 MDF_PA13_HIGH = 1
 
+MDF4K_AUTOSTART_DELAY = 60
+
 test_good_phase := test_state+6
 
 OAM := $0200  ; for synced reads
@@ -111,15 +113,58 @@ irq_handler:
   sta mdfourier_good_phase
   lda #VBLANK_NMI
   sta PPUCTRL
-  .ifdef ::MDF4K_AUTOSTART
-    jmp autostart_entry_point
-  .else
+  .ifndef ::MDF4K_AUTOSTART
     jsr mdfourier_ready_tone
   .endif
 
 restart:
   jsr mdfourier_init_apu
   jsr mdfourier_push_apu
+  jsr mdf4k_draw_title
+
+  .ifdef ::MDF4K_AUTOSTART
+    ldy #MDF4K_AUTOSTART_DELAY
+    titlewait:
+      jsr vsync
+      dey
+      bne titlewait
+  .else
+    ; Wait for A press
+    keywait:
+      jsr read_pads
+      jsr vsync
+      lda new_keys
+      bpl keywait
+  .endif
+
+autostart_entry_point:
+  ; reduce interference from the PPU as far as we possibly can
+  ldy #$3F
+  lda #$00
+  ldx #$0D
+  sta PPUMASK
+  sty PPUADDR
+  sta PPUADDR
+  stx PPUDATA
+  sta PPUADDR
+  sta PPUADDR
+
+  .if ::MDF_PA13_HIGH
+    ldx #$20
+    stx PPUADDR
+    sta PPUADDR
+  .endif
+  jsr mdfourier_run
+
+  .ifdef ::MDF4K_AUTOSTART
+    jsr mdf4k_draw_title
+  forever: jmp forever
+  .else
+    jmp restart
+  .endif
+.endproc
+
+.proc mdf4k_draw_title
   lda #VBLANK_NMI
   sta PPUCTRL
   asl a
@@ -212,33 +257,7 @@ have_phase_xy:
   sta PPUSCROLL
   lda #BG_ON
   sta PPUMASK
-
-  ; Wait for A press
-  keywait:
-    jsr read_pads
-    jsr vsync
-    lda new_keys
-    bpl keywait
-
-autostart_entry_point:
-  ; reduce interference from the PPU as far as we possibly can
-  ldy #$3F
-  lda #$00
-  ldx #$0D
-  sta PPUMASK
-  sty PPUADDR
-  sta PPUADDR
-  stx PPUDATA
-  sta PPUADDR
-  sta PPUADDR
-
-  .if ::MDF_PA13_HIGH
-    ldx #$20
-    stx PPUADDR
-    sta PPUADDR
-  .endif
-  jsr mdfourier_run
-  jmp restart
+  rts
 .endproc
 
 .proc write_4y_of_a
@@ -261,14 +280,21 @@ autostart_entry_point:
 .endproc
 
 .proc mdfourier_present
-  bit new_keys
-  bvc no_B_press
-    lda mdfourier_good_phase
-    sta test_good_phase
-    rts
-  no_B_press:
-  jsr vsync
-  jsr sync_read_b_button
+  .ifdef ::MDF4K_AUTOSTART
+    jsr vsync
+    lda #0
+    sta new_keys
+    sta cur_keys
+  .else
+    bit new_keys
+    bvc no_B_press
+      lda mdfourier_good_phase
+      sta test_good_phase
+      rts
+    no_B_press:
+    jsr vsync
+    jsr sync_read_b_button
+  .endif
   jmp mdfourier_push_apu
 .endproc
 
@@ -290,4 +316,4 @@ chrdata_end:
 
 .rodata
 uipalette: .byte $0F, $20, $0F, $20, $0F, $0F, $10, $10
-uipalette_end:
+uipalette_end: