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@ Copyright 2022 Gabriel Jensen.
@ This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
@ If a copy of the MPL was not distributed with this file, You can obtain one at https://mozilla.org/MPL/2.0/.
.syntax unified
.cpu arm7tdmi
.thumb
.globl ax_vsync
.func
.thumb_func
ax_vsync:
@ Set the constants:
ldr r0,.vcountaddr @ ax_i20 vcountaddr = 0x4000006u;
movs r1,0xA0 @ ax_i20 numhline = 0xA0;
.loop:
@ Check the scanline counter:
ldrh r2,[r0] @ ax_i20 vcount = *(ax_i10 *)vcountaddr;
cmp r2,r1
beq .ret @ if (vcount == numhline) {goto ret;}
b .loop @ goto loop;
.ret:
@ Return:
bx lr @ return;
.endfunc
.align
.vcountaddr:
.long 0x4000006
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