Use DMA

2022-06-17 14:37:10 -07:00 · 2022-06-17 14:37:10 -07:00 · 63f37f69af
commit 63f37f69af
parent 1c6fdd3468
1 changed files with 34 additions and 9 deletions
--- a/homebrew-tutorial/main.asm
+++ b/homebrew-tutorial/main.asm
@ -60,15 +60,40 @@ start:
    sta VMAIN
    ldx #VRAM_CHARS
    stx VMADDL
-@charset_loop:
-    lda charset,x
-    sta VMDATAL
-    inx
-    lda charset,x
-    sta VMDATAH
-    inx
-    cpx #(charset_end - charset)
-    bne @charset_loop
+
+    ; Set DMA source flags
+    lda #%00000001
+    sta DMAP0
+
+    ; DMA destination VMDATAL register
+    lda #<VMDATAL
+    sta BBAD0
+
+    ; Set starting address to charset
+    ldx #.loword(charset)
+    stx A1T0L
+    lda #^charset
+    sta A1B0
+
+    ; Write to charset_end bytes
+    ldx #(charset_end - charset)
+    stx DAS0L
+
+    ; actually kick off the DMA
+    lda #1
+    sta MDMAEN
+
+
+
+; @charset_loop:
+;     lda charset,x
+;     sta VMDATAL
+;     inx
+;     lda charset,x
+;     sta VMDATAH
+;     inx
+;     cpx #(charset_end - charset)
+;     bne @charset_loop

 ; Manually clear screen
    ldx #(VRAM_BG1)