.arm
.section .text
.org 0x08000000 @@ game pak
.global _start
.global halt
.global initscr
.global bitblt
.global vtrace
_start:
mrs r0, cpsr
and r1, r0, #0x1F
cmp r1, #0x1F
orrne r0, r0, #0x1F
msrne cpsr_c, r0
mov sp, #0x08000000
add sp, sp, #0x00001000 @@ 64 KiB descending stack
bl initscr
mloop:
bl bitblt
bl vtrace
b mloop

vtrace:
swi #0x5
mov pc, lr

halt:
swi #0x2
mov pc, lr

initscr:
stmfd sp!, {r0-r1}
mov r0, #0x0
orr r0, r0, #0x3 @@ Set video mode 3, 240x160 16-bit bitmapped
mov r1, #0x04000000
ldr r1, [r0]
ldmia sp!, {r0-r1}
mov pc, lr

bitblt:
stmfd sp!, {r0-r2}
mov r0, #0x06000000 @@ framebuffer base
add r1, r0, #0x12C00 @@ framebuffer base + size
mov r2, #31
blitloop:
strh r2, [r0]
add r0, r0, #2
cmp r0, r1
subne pc, pc, #20 @@ ble blitloop
ldmia sp!, {r0-r2}
mov pc, lr