Works perfectly:
----------------

start

waitrast
lda #$40
cmp $d012
bne waitrast
waitrast2
lda #$41
cmp $d012
bne waitrast2

cpy #$01
beq down

up
inc $d011
inx
cpx #$02
bne start
ldy #$01
jmp start

down
dec $d011
dex
bne start

Doesn't work from within a raster IRQ
-------------------------------------

IRQ
LDA $D019
AND #$01
STA $D019

cpy #$01
beq down

up
inc $d011
inx
cpx #$02
bne end
ldy #$01
jmp $ea7e

down
dec $d011
dex
bne end
ldy #$00

end
JMP $EA7E
ldy #$00

JMP start