dofile "vcs.lua"

TIM_OVERSCAN    = 50 -- TIM64T,  3200 cycles = ~ 42 scanlines
TIM_VBLANK      = 61 -- TIM64T,  3904 cycles = ~ 51 scanlines
TIM_KERNEL      = 17 -- T1024T, 17408 cycles = ~229 scanlines

location(0xf000, 0xffff)

local kernel = function()
    ldx#0xd0 @_loop sta WSYNC stx COLUBK dex bne _loop
end

local wait = function() local l=label() lda INTIM bne l end

@@start
    -- clear zeropage
    cld ldx#0 txa @_clear dex tsx pha bne _clear
@main
    -- overscan
    sta WSYNC lda#2 sta VBLANK lda#TIM_OVERSCAN sta TIM64T wait()
    -- vblank
    lda#0b1110 @_vsync sta WSYNC sta VSYNC lsr bne _vsync
    lda#2 sta VBLANK lda#TIM_VBLANK sta TIM64T wait() sta WSYNC sta VBLANK
    -- kernel
    lda#TIM_KERNEL sta T1024T kernel() wait()
    jmp main

section{'vectors', org=0xfffc} word(start,start)

local filename=string.match(arg[0], ".-([^\\/]-)%.?[^%.\\/]*$")
writebin(filename..'.bin')
writesym(filename..'.sym')
print(stats)