1 files changed, 39 insertions, 0 deletions
diff --git a/00-disptest/start.S b/00-disptest/start.S
new file mode 100644
index 0000000..aee4759
--- /dev/null
+++ b/00-disptest/start.S
@@ -0,0 +1,39 @@
+#define VRAMADDR 0x14800000
+#define DISPH 480
+#define DISPW 800
+
+.globl start
+.arm
+start:
+// r0: y, r1: x
+  mov r0, #0
+  mov r1, #0
+
+.Lloopy:
+  cmp r0, #(DISPH)
+  beq .Lstop
+.Lloopx:
+  cmp r1, #(DISPW)
+  bne .Lcontx
+  mov r1, #0
+  add r0, #1
+  b .Lloopy
+.Lcontx:
+// r2: ((y&0)^(x&0)) ? 0xffffffff : 0
+  eor r2, r0, r1
+  and r2, #1
+  sub r2, #1
+// addr: VRAMADDR + (y*DISPW + x)*2
+  mov r3, #(DISPW)
+  mul r3, r0
+  add r3, r1
+  add r3, r3
+  add r3, #(VRAMADDR)
+// store the pixel
+  strh r2, [r3]
+
+  add r1, #1
+  b .Lloopx
+.Lstop:
+  b .Lstop
+