l65/samples/vcs_hooks.l65

require'vcs'

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)

section{'vectors', org=0xfffc} dc.w start,start

local kernel = function()
    -- add a dummy instruction to collect cycle count and binary size
    local kernel_cycles,kernel_size
    table.insert(section_current.instructions, { bin=function() kernel_cycles=cycles kernel_size=size end })
 
    samepage
        ldx#0xd0 @_loop sta WSYNC stx COLUBK dex bne _loop
    end

    -- and get the delta (cycles are counted without taking any branch)
    table.insert(section_current.instructions, { bin=function() print('kernel cycles: ', cycles-kernel_cycles, 'kernel size: ', size-kernel_size) end })
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
;
writebin(filename..'.bin')
writesym(filename..'.sym')
print(stats)