diff options
| -rw-r--r-- | basics/flicker.s | 3 | ||||
| -rw-r--r-- | fx/blink.s | 3 | ||||
| -rw-r--r-- | scroll/roulette.s | 5 | ||||
| -rw-r--r-- | shared/clear.s | 39 |
4 files changed, 50 insertions, 0 deletions
diff --git a/basics/flicker.s b/basics/flicker.s index 234c8a1..8db03e8 100644 --- a/basics/flicker.s +++ b/basics/flicker.s @@ -21,8 +21,11 @@ .segment "CODE" .include "../shared/diskun.s" +.include "../shared/clear.s" .proc main + CLEAR_SCREEN + jsr Diskun::init_palettes jsr init_sprites @@ -122,6 +122,7 @@ ;;; player around. .segment "FIXED" .include "../shared/diskun.s" +.include "../shared/clear.s" ;;; NOTE: the main bulk of this example. Comments only for the parts which are ;;; specific to this example. @@ -252,6 +253,8 @@ reset: lda #4 sta Vars::last_bank + CLEAR_SCREEN + jsr Diskun::init_palettes jsr init_sprites diff --git a/scroll/roulette.s b/scroll/roulette.s index 4b13c22..aca7d72 100644 --- a/scroll/roulette.s +++ b/scroll/roulette.s @@ -107,6 +107,7 @@ ;;; player around. .segment "FIXED" .include "../shared/diskun.s" +.include "../shared/clear.s" ;;; NOTE: the main bulk of this example. Comments only for the parts which are ;;; specific to this example. @@ -201,6 +202,10 @@ reset: ;; The main function is used here only for further initialization purposes. .proc main + ;; Clear both screens to avoid funky business, as we are not doing anything + ;; specially clever here. + CLEAR_SCREENS $20, $24 + ;; Initialize both the palettes and the nametables. jsr Diskun::init_palettes jsr init_nametables diff --git a/shared/clear.s b/shared/clear.s new file mode 100644 index 0000000..a099387 --- /dev/null +++ b/shared/clear.s @@ -0,0 +1,39 @@ +;; Clear the first nametable by resetting it to the default tile ID. This is a +;; rather drastic measure only to be done on examples that don't actually load +;; columns in "clever" ways, but they just want a clean slate. +.macro CLEAR_SCREEN + ldy #$20 + jsr clear_screen_y +.endmacro + +;; Clear the given two nametables. `ONE` and `OTHER` have to be the high byte +;; for each nametable to clear. For example, on an horizontal scrolling game: +;; `CLEAR_SCREENS $20, $24`. +.macro CLEAR_SCREENS ONE, OTHER + ldy #ONE + jsr clear_screen_y + + ldy #OTHER + jsr clear_screen_y +.endmacro + +;; Clear the nametable with the high byte as defined in the `y` register. +.proc clear_screen_y + bit $2002 + + ldx #$FF +@loop: + sty $2006 + stx $2006 + lda #$00 + sta $2007 + + dex + bne @loop + + iny + cpy #$24 + bne @loop + + rts +.endproc |