Added the VM player using SDL

- Wired basic functionality (fram-buffer, frame interrupt)
- Bug fixes in the assembler

1 files changed, 37 insertions, 100 deletions

diff --git a/example.asm b/example.asm
index 6d4521e..d96277b 100644
--- a/example.asm
+++ b/example.asm
@@ -3,54 +3,44 @@
 ;
 .org 0
 
-;     ; copy 16K from 0x0000 to 0xbf00
-;     ;
-; start:
-;     ld a, 0
-;     ld b, 0xbf
-;     ld x, 0
-;     ld y, 0x40
-; loop:
-;     push y
-;     ld y, [a : x]
-;     ld [b : x], y
-;     pop y
-;     inc x
-;     bno
-;     jmp loop
-;     inc a
-;     inc b
-;     dec y
-;     bnz
-;     jmp loop
-;
-    ld b, 15
+    ; setup an int handler so we
+    ; can use the frame int to sync
+    ld a, 0xff
+    ld x, 0
+    ld b, <int_handler
+    ld [a : x], b
+    inc x
+    ld b, >int_handler
+    ld [a : x], b
+
+    ; enable interrupts
+    cif
+
+    ; loop filling the screen with one
+    ; colour cycling the whole palette
+    ld b, 0
+loop:
     call fill
+    inc b
+    and b, 15
 
+    ; wait some frames
+    halt
+    halt
+    halt
+    halt
+
+    halt
+    halt
+    halt
     halt
-;
-;     ; void copy(void *dst, void *src, uint16_t size)
-;     ; size = 0x1000
-;     ; src = 0
-;     ; dst 0xbf00
-;     ld a, 0x10
-;     push a
-;     ld a, 0
-;     push a
-;     push a
-;     push a
-;     ld a, 0xbf
-;     push a
-;     ld a, 0
-;     push a
-;     call copy
-;     pop a
-;     pop a
-;     pop a
-;     pop a
-;     pop a
-;     pop a
-;     halt
+
+    halt
+    halt
+    halt
+    halt
+
+    jmp loop
 
     ; fill frame-buffer with a color in reg b
 fill:
@@ -68,58 +58,5 @@ fill_loop:
     jmp fill_loop
     ret
 
-    ; void copy(void *dst, void *src, uint16_t size)
-    ;
-    ; using C calling convention with the stack
-    ; not used, but return value in a (8-bit), a: x (16-bit)
-; copy:
-;     ld x, [sp + 6]
-;     ld a, [sp + 7] ; size a:x
-;
-;     ; local variable
-;     push a
-;     push x
-;
-;     ld y, [sp + 4]
-;     ld b, [sp + 5] ; dst b:y
-;     ld x, [sp + 6]
-;     ld a, [sp + 7] ; src a:x
-; copy_loop:
-;     ; copy byte from a:x to b:y
-;     push x
-;     ld x, [a : x]
-;     ld [b : y], x
-;     pop x
-;
-;     ; inc a:x
-;     inc x
-;     bo
-;     inc a
-;
-;     ; inc b:y
-;     inc y
-;     bo
-;     inc b
-;
-;     ; dec local var size
-;     push a
-;     push x
-;     ld x, [sp + 2]
-;     ld a, [sp + 3]
-;     dec x
-;     bo
-;     dec a
-;     ld [sp + 2], x
-;     ld [sp + 3], a
-;     or x, a
-;     pop x
-;     pop a
-;
-;     bnz
-;     jmp copy_loop
-;
-;     pop x
-;     pop x ; free local var
-;     ret
-;
-;
+int_handler:
+    iret