From 4db3c9071d5a22123f3ee0d49ce709c47c4a4a71 Mon Sep 17 00:00:00 2001
From: not_a_robot06 <temporarythrowaway@tutamail.com>
Date: Sat, 15 Feb 2025 19:56:14 +0000
Subject: use chrout to clear screen

- turns out there are kernal routines for handling cursors and printing
  so is the proper way to do things
---
 life.asm | 35 +++++------------------------------
 1 file changed, 5 insertions(+), 30 deletions(-)

(limited to 'life.asm')

diff --git a/life.asm b/life.asm
index 1e3a6af..2745dc6 100644
--- a/life.asm
+++ b/life.asm
@@ -5,10 +5,14 @@ numL := $02 ; low byte of a 16-bit number
 numH := $03 ; low byte of a 16-bit number
 key_buf_len := $c6
 key_buf := $0277
+CHROUT := $ffd2
 
 ; initialisation: clear screen and set num to point to screen mem start
 init:
-  jsr clear_screen
+  ; clear screen
+  lda #$93
+  jsr CHROUT
+
   ldy #$00
   lda #$04
   sta numH
@@ -77,35 +81,6 @@ key_wait_loop:
   pla
   rts
 
-; clear the screen by filling it with spaces
-; destroys: A, Y, numL & numH (in memory)
-clear_screen:
-  ; init: y = 0 because you can't use indirect addressing without a register,
-  ; load start of screen memory into numL/numH
-  ldy #0
-  lda #$04
-  sta numH
-  lda #$00
-  sta numL
-  jmp cs_loop
-
-  ; add 1 to high bit, return if $08 (screen mem only goes to $07ff)
-  add_carry:
-    inc numH
-    lda numH
-    cmp #$08
-    bne cs_loop
-    rts
-
-  ; store a space in current screen mem address as specified by num, branch if
-  ; number overflows to 0 (i.e. add 1 to high bit of 16 bit number)
-  cs_loop:
-    lda #$20
-    sta (numL),y
-    inc numL
-    beq add_carry
-    jmp cs_loop
-
 ; print byte in A at location in num
 print_byte:
   ; init: store original A in X and push Y to stack
-- 
cgit v1.2.3