If you want an example in sc4
use magoo's vscreen.
It is the best opensource project I have ever seen for a platworm
and in my opinion can be easly adapted to a shoot'em up like spacemambow

platworm or lintworm?

*sorry*

I still have some problems with replacing my sprites and scrolling the screen.

I first wait until start of VBLANK with reading status register VR bit.
if it is not set status register is read again and again until VR bit is set.

then I scroll my screen and (rapidly) replace all my sprites.

between some line (lets say between y=100 and y=130 it the sprites still flicker.

Is this my emulator? I still have doubts about reading status register VR bit.
Im not sure if im doing it good. I read all the articles.

First I set the status register number in register 15,
and this in a,($98) and then I bit 6,a until a=1
(if im not mistakin)
after this i reset register 15

though, doing this, or not doing this doesnt seem to make much difference.....

It should pretty much work like that. There really shouldn't be any flickering in that case either... If you're using blueMSX or openMSX the emulator shouldn't cause the flickering either... Are you sure you don't exceed the limit of 8 sprites/row? That can cause odd sprite behaviour...

It's very hard doing debug in this way.
Have you seen the magoo's webpage and code?

The actuall screen replacement (set adjust + sprites and such) should take place on interrupt (either polling (like u do) or real interrupt calling) and nothing more. so pre calculate all stuff. when doing quick vdp settings (that means NO copying of big gfx for example) it will work perfectly.

When you say much flikkering exists at about 1/3 of the screen it simply means your routine is too slow or has massive other (non vpd) action (like a music replayer) going on BEFORE the actuall adjust/sprite settings.

Could you tell me a bit about Real interrupt calling.
*is this like the oninterval thing basic uses?