diff options
Diffstat (limited to 'agbx/source/gfx/getvbnk.s')
| -rw-r--r-- | agbx/source/gfx/getvbnk.s | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/agbx/source/gfx/getvbnk.s b/agbx/source/gfx/getvbnk.s new file mode 100644 index 0000000..e04a127 --- /dev/null +++ b/agbx/source/gfx/getvbnk.s @@ -0,0 +1,65 @@ +@ 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 __agbx_getvbnk +.globl agbx_getvbnk + +.func + +.thumb_func + +agbx_getvbnk: + @ Get the current value of dispcnt: + ldr r0,.dispcntaddr + ldrh r1,[r0] + + @ Get the address: + b __agbx_getvbnk + + bx lr + +.endfunc + +.func + +.thumb_func + +__agbx_getvbnk: @ Takes the value of dispcnt in r1. + @ Check if the fifth bit is set: + movs r0,0b10000 + tst r1,r0 + + bne .vbnk1 + +.vbnk0: + @ Return the address of the first video bank: + ldr r0,.vbnk0addr + bx lr + +.vbnk1: + @ Return the address of the second video bank: + ldr r0,.vbnk1addr + bx lr + +.endfunc + +.align + +.dispcntaddr: + .long 0x4000000 + +.align + +.vbnk0addr: + .long 0x6000000 + +.align + +.vbnk1addr: + .long 0x600A000 |